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Sample records for pseudo-continuous arterial spin

  1. Unilateral fetal-type circle of Willis anatomy causes right-left asymmetry in cerebral blood flow with pseudo-continuous arterial spin labeling: A limitation of arterial spin labeling-based cerebral blood flow measurements?

    PubMed

    Barkeij Wolf, Jurriaan Jh; Foster-Dingley, Jessica C; Moonen, Justine Ef; van Osch, Matthias Jp; de Craen, Anton Jm; de Ruijter, Wouter; van der Mast, Roos C; van der Grond, Jeroen

    2016-09-01

    The accuracy of cerebral blood flow measurements using pseudo-continuous arterial spin labeling can be affected by vascular factors other than cerebral blood flow, such as flow velocity and arterial transit time. We aimed to elucidate the effects of common variations in vascular anatomy of the circle of Willis on pseudo-continuous arterial spin labeling signal. In addition, we investigated whether possible differences in pseudo-continuous arterial spin labeling signal could be mediated by differences in flow velocities. Two hundred and three elderly participants underwent magnetic resonance angiography of the circle of Willis and pseudo-continuous arterial spin labeling scans. Mean pseudo-continuous arterial spin labeling-cerebral blood flow signal was calculated for the gray matter of the main cerebral flow territories. Mean cerebellar gray matter pseudo-continuous arterial spin labeling-cerebral blood flow was significantly lower in subjects having a posterior fetal circle of Willis variant with an absent P1 segment. The posterior fetal circle of Willis variants also showed a significantly higher pseudo-continuous arterial spin labeling-cerebral blood flow signal in the ipsilateral flow territory of the posterior cerebral artery. Flow velocity in the basilar artery was significantly lower in these posterior fetal circle of Willis variants. This study indicates that pseudo-continuous arterial spin labeling measurements underestimate cerebral blood flow in the posterior flow territories and cerebellum of subjects with a highly prevalent variation in circle of Willis morphology. Additionally, our data suggest that this effect is mediated by concomitant differences in flow velocity between the supplying arteries.

  2. Feasibility of Using Pseudo-Continuous Arterial Spin Labeling Perfusion in a Geriatric Population at 1.5 Tesla

    PubMed Central

    Sigurdsson, Sigurdur; Forsberg, Lars; Aspelund, Thor; van der Geest, Rob J.; van Buchem, Mark A.; Launer, Lenore J.; Gudnason, Vilmundur; van Osch, Matthias J.

    2015-01-01

    Objectives To evaluate the feasibility of using pseudo-continuous arterial spin labeling (pCASL) perfusion in a geriatric population at 1.5-Tesla. Materials and Methods In 17 participants (mean age 78.8±1.63 years) we assessed; 1) inter-session repeatability and reliability of resting state perfusion in 27 brain regions; 2) brain activation using finger-tapping as a means to evaluate the ability to detect flow differences; 3) reliability by comparing cerebral blood flow (CBF) with pCASL to CBF with phase contrast (PC-MR). Results The CBF (mean±standard deviation (SD)) for the whole brain grey matter (GM) was 40.6±8.4 and 41.4±8.7 ml/100g/min for the first and second scan respectively. The within-subject standard deviation (SDw), the repeatability index (RI) and intra-class correlation coefficient (ICC) across the 27 regions ranged from 1.1 to 7.9, 2.2 to 15.5 and 0.35 to 0.98 respectively. For whole brain GM the SDw, RI and ICC were 1.6, 3.2 and 0.96 respectively. The between-subject standard deviation (SDB) was larger than the SDw for all regions. Comparison of CBF at rest and activation on a voxel level showed significantly higher perfusion during finger tapping in the motor- and somatosensory regions. The mean CBF for whole brain GM was 40.6±8.4 ml/100g/min at rest and 42.6±8.6 ml/100g/min during activation. Finally the reliability of pCASL against the reference standard of PC-MR was high (ICC = 0.80). The mean CBF for whole brain measured with PC-MRI was 54.3±10.1 ml/100g/min and 38.3±7.8 ml/100g/min with pCASL. Conclusions The results demonstrate moderate to high levels of repeatability and reliability for most brain regions, comparable to what has been reported for younger populations. The performance of pCASL at 1.5-Tesla shows that region-specific perfusion measurements with this technique are feasible in studies of a geriatric population. PMID:26659363

  3. Simultaneous multi-slice Turbo-FLASH imaging with CAIPIRINHA for whole brain distortion-free pseudo-continuous arterial spin labeling at 3 and 7 T.

    PubMed

    Wang, Yi; Moeller, Steen; Li, Xiufeng; Vu, An T; Krasileva, Kate; Ugurbil, Kamil; Yacoub, Essa; Wang, Danny J J

    2015-06-01

    Simultaneous multi-slice (SMS) or multiband (MB) imaging has recently been attempted for arterial spin labeled (ASL) perfusion MRI in conjunction with echo-planar imaging (EPI) readout. It was found that SMS-EPI can reduce the T1 relaxation effect of the label and improve image coverage and resolution with little penalty in signal-to-noise ratio (SNR). However, EPI still suffers from geometric distortion and signal dropout from field inhomogeneity effects especially at high and ultrahigh magnetic fields. Here we present a novel scheme for achieving high fidelity distortion-free quantitative perfusion imaging by combining pseudo-continuous ASL (pCASL) with SMS Turbo-FLASH (TFL) readout at both 3 and 7 T. Bloch equation simulation was performed to characterize and optimize the TFL-based pCASL perfusion signal. Two MB factors (3 and 5) were implemented in SMS-TFL pCASL and compared with standard 2D TFL and EPI pCASL sequences. The temporal SNR of SMS-TFL pCASL relative to that of standard TFL pCASL was 0.76 ± 0.10 and 0.74 ± 0.11 at 7 T and 0.70 ± 0.05 and 0.65 ± 0.05 at 3T for MB factor of 3 and 5, respectively. By implementing background suppression in conjunction with SMS-TFL at 3T, the relative temporal SNR improved to 0.84 ± 0.09 and 0.79 ± 0.10 for MB factor of 3 and 5, respectively. Compared to EPI pCASL, significantly increased temporal SNR (p<0.001) and improved visualization of orbitofrontal cortex were achieved using SMS-TFL pCASL. By combining SMS acceleration with TFL pCASL, we demonstrated the feasibility for whole brain distortion-free quantitative mapping of cerebral blood flow at high and ultrahigh magnetic fields.

  4. Simultaneous Multi-slice Turbo-FLASH Imaging with CAIPIRINHA for Whole Brain Distortion-Free Pseudo-Continuous Arterial Spin Labeling at 3 and 7T

    PubMed Central

    Wang, Yi; Moeller, Steen; Li, Xiufeng; Vu, An T.; Krasileva, Kate; Ugurbil, Kamil; Yacoub, Essa; Wang, Danny JJ

    2015-01-01

    Simultaneous multi-slice (SMS) or multiband (MB) imaging has recently been attempted for arterial spin labeled (ASL) perfusion MRI in conjunction with echo-planar imaging (EPI) readout. It was found that SMS-EPI can reduce the T1 relaxation effect of the label, improve image coverage and resolution with little penalty in signal-to-noise ratio (SNR). However, EPI still suffers from geometric distortion and signal dropout from field inhomogeneity effects especially at high and ultrahigh magnetic fields. Here we present a novel scheme for achieving high fidelity distortion-free quantitative perfusion imaging by combining pseudo-continuous ASL (pCASL) with SMS Turbo-FLASH (TFL) readout at both 3 and 7 Tesla. Bloch equation simulation was performed to characterize and optimize the TFL-based pCASL perfusion signal. Two MB factors (3 and 5) were implemented in SMS-TFL pCASL and compared with standard 2D TFL and EPI pCASL sequences. The temporal SNR of SMS-TFL pCASL relative to that of standard TFL pCASL was 0.76±0.10 and 0.74±0.11 at 7T, 0.70±0.05 and 0.65±0.05 at 3T for MB factor of 3 and 5, respectively. By implementing background suppression in conjunction with SMS-TFL at 3T, the relative temporal SNR improved to 0.84±0.09 and 0.79±0.10 for MB factor of 3 and 5 respectively. Compared to EPI pCASL, significantly increased temporal SNR (p<0.001) and improved visualization of orbitofrontal cortex were achieved using SMS-TFL pCASL. By combining SMS acceleration with TFL pCASL, we demonstrated the feasibility for whole brain distortion-free quantitative mapping of cerebral blood flow at high and ultrahigh magnetic fields. PMID:25837601

  5. Acceleration-selective arterial spin labeling.

    PubMed

    Schmid, Sophie; Ghariq, Eidrees; Teeuwisse, Wouter M; Webb, Andrew; van Osch, Matthias J P

    2014-01-01

    In this study, a new arterial spin labeling (ASL) method with spatially nonselective labeling is introduced, based on the acceleration of flowing spins, which is able to image brain perfusion with minimal contamination from venous signal. This method is termed acceleration-selective ASL (AccASL) and resembles velocity-selective ASL (VSASL), with the difference that AccASL is able to discriminate between arterial and venous components in a single preparation module due to the higher acceleration on the arterial side of the microvasculature, whereas VSASL cannot make this distinction unless a second labeling module is used. A difference between AccASL and VSASL is that AccASL is mainly cerebral blood volume weighted, whereas VSASL is cerebral blood flow weighted. AccASL exploits the principles of acceleration-encoded magnetic resonance angiography by using motion-sensitizing gradients in a T2 -preparation module. This method is demonstrated in healthy volunteers for a range of cutoff accelerations. Additionally, AccASL is compared with VSASL and pseudo-continuous ASL, and its feasibility in functional MRI is demonstrated. Compared with VSASL with a single labeling module, a strong and significant reduction in venous label is observed. The resulting signal-to-noise ratio is comparable to pseudo-continuous ASL and robust activation of the visual cortex is observed.

  6. SU-E-I-65: Estimation of Tagging Efficiency in Pseudo-Continuous Arterial Spin Labeling (pCASL) MRI

    SciTech Connect

    Jen, M; Yan, F; Tseng, Y; Chen, C; Lin, C; Liu, H

    2015-06-15

    Purpose: pCASL was recommended as a potent approach for absolute cerebral blood flow (CBF) quantification in clinical practice. However, uncertainties of tagging efficiency in pCASL remain an issue. This study aimed to estimate tagging efficiency by using short quantitative pulsed ASL scan (FAIR-QUIPSSII) and compare resultant CBF values with those calibrated by using 2D Phase Contrast (PC) MRI. Methods: Fourteen normal volunteers participated in this study. All images, including whole brain (WB) pCASL, WB FAIR-QUIPSSII and single-slice 2D PC, were collected on a 3T clinical MRI scanner with a 8-channel head coil. DeltaM map was calculated by averaging the subtraction of tag/control pairs in pCASL and FAIR-QUIPSSII images and used for CBF calculation. Tagging efficiency was then calculated by the ratio of mean gray matter CBF obtained from pCASL and FAIR-QUIPSSII. For comparison, tagging efficiency was also estimated with 2D PC, a previously established method, by contrast WB CBF in pCASL and 2D PC. Feasibility of estimation from a short FAIR-QUIPSSII scan was evaluated by number of averages required for obtaining a stable deltaM value. Setting deltaM calculated by maximum number of averaging (50 pairs) as reference, stable results were defined within ±10% variation. Results: Tagging efficiencies obtained by 2D PC MRI (0.732±0.092) were significantly lower than which obtained by FAIRQUIPPSSII (0.846±0.097) (P<0.05). Feasibility results revealed that four pairs of images in FAIR-QUIPPSSII scan were sufficient to obtain a robust calibration of less than 10% differences from using 50 pairs. Conclusion: This study found that reliable estimation of tagging efficiency could be obtained by a few pairs of FAIR-QUIPSSII images, which suggested that calibration scan in a short duration (within 30s) was feasible. Considering recent reports concerning variability of PC MRI-based calibration, this study proposed an effective alternative for CBF quantification with pCASL.

  7. Can arterial spin labeling detect white matter perfusion signal?

    PubMed

    van Osch, Matthias J P; Teeuwisse, Wouter M; van Walderveen, Marianne A A; Hendrikse, Jeroen; Kies, Dennis A; van Buchem, Mark A

    2009-07-01

    Since the invention of arterial spin labeling (ASL) it has been acknowledged that ASL does not allow reliable detection of a white matter (WM) perfusion signal. However, recent developments such as pseudo-continuous labeling and background suppression have improved the quality. The goal of this research was to study the ability of these newer ASL sequences to detect WM perfusion signal. Background suppressed pseudo-continuous ASL was implemented at 3T with multislice 2D readout after 1525 ms. In five volunteers it was shown that 10 min scanning resulted in significant perfusion signal in 70% of WM voxels. Increasing the labeling and delay time did not lead to a higher percentage. In 27 normal volunteers it was found that 35 averages are necessary to detect significant WM signal, but 150 averages are needed to detect signal in the deep WM. Finally, it was shown in a patient with a cerebral arteriovenous malformation that pseudo-continuous ASL enabled the depiction of hypointense WM perfusion signal, although dynamic susceptibility contrast MRI showed that this region was merely showing delayed arrival of contrast agent than hypoperfusion. It can be concluded that, except within the deep WM, ASL is sensitive enough to detect WM perfusion signal and perfusion deficits. PMID:19365865

  8. Pseudo-continuous-wave acoustic instrument

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.; Stone, F. D.

    1978-01-01

    Simple, inexpensive, and portable ultrasonic device accurately measures acoustic properties of liquids, gases, and solids, using pseudo-continuous wave responses from samples to measure change in resonant frequency or amplitude in acoustic signal.

  9. Clinical applications of arterial spin labeling.

    PubMed

    Watts, Jonathan M; Whitlow, Christopher T; Maldjian, Joseph A

    2013-08-01

    MR arterial spin labeling is primarily applied as a neuroimaging method to measure cerebral blood flow. As this technique becomes more widely available, a basic understanding of the clinical applications is necessary for optimal utilization in the setting of patient care. This review focuses on the use of arterial spin labeling imaging for the evaluation of cerebrovascular disease, brain tumors and neuropsychiatric illness. PMID:23378178

  10. Rapid 3D dynamic arterial spin labeling with a sparse model-based image reconstruction.

    PubMed

    Zhao, Li; Fielden, Samuel W; Feng, Xue; Wintermark, Max; Mugler, John P; Meyer, Craig H

    2015-11-01

    Dynamic arterial spin labeling (ASL) MRI measures the perfusion bolus at multiple observation times and yields accurate estimates of cerebral blood flow in the presence of variations in arterial transit time. ASL has intrinsically low signal-to-noise ratio (SNR) and is sensitive to motion, so that extensive signal averaging is typically required, leading to long scan times for dynamic ASL. The goal of this study was to develop an accelerated dynamic ASL method with improved SNR and robustness to motion using a model-based image reconstruction that exploits the inherent sparsity of dynamic ASL data. The first component of this method is a single-shot 3D turbo spin echo spiral pulse sequence accelerated using a combination of parallel imaging and compressed sensing. This pulse sequence was then incorporated into a dynamic pseudo continuous ASL acquisition acquired at multiple observation times, and the resulting images were jointly reconstructed enforcing a model of potential perfusion time courses. Performance of the technique was verified using a numerical phantom and it was validated on normal volunteers on a 3-Tesla scanner. In simulation, a spatial sparsity constraint improved SNR and reduced estimation errors. Combined with a model-based sparsity constraint, the proposed method further improved SNR, reduced estimation error and suppressed motion artifacts. Experimentally, the proposed method resulted in significant improvements, with scan times as short as 20s per time point. These results suggest that the model-based image reconstruction enables rapid dynamic ASL with improved accuracy and robustness.

  11. Noninvasive assessment of arterial compliance of human cerebral arteries with short inversion time arterial spin labeling.

    PubMed

    Warnert, Esther A H; Murphy, Kevin; Hall, Judith E; Wise, Richard G

    2015-03-01

    A noninvasive method of assessing cerebral arterial compliance (AC) is introduced in which arterial spin labeling (ASL) is used to measure changes in arterial blood volume (aBV) occurring within the cardiac cycle. Short inversion time pulsed ASL (PASL) was performed in healthy volunteers with inversion times ranging from 250 to 850 ms. A model of the arterial input function was used to obtain the cerebral aBV. Results indicate that aBV depends on the cardiac phase of the arteries in the imaging volume. Cerebral AC, estimated from aBV and brachial blood pressure measured noninvasively in systole and diastole, was assessed in the flow territories of the basal cerebral arteries originating from the circle of Willis: right and left middle cerebral arteries (RMCA and LMCA), right and left posterior cerebral arteries (RPCA and LPCA), and the anterior cerebral artery (ACA). Group average AC values calculated for the RMCA, LMCA, ACA, RPCA, and LPCA were 0.56%±0.2%, 0.50%±0.3%, 0.4%±0.2%, 1.1%±0.5%, and 1.1%±0.3% per mm Hg, respectively. The current experiment has shown the feasibility of measuring AC of cerebral arteries with short inversion time PASL.

  12. Pseudo-continuous-time quadratic regulators with pole placement in a specific region

    NASA Technical Reports Server (NTRS)

    Shieh, L. S.; Zhang, J. L.; Ganesan, S.

    1990-01-01

    The paper comments on the pseudo-continuous-time quadratic regulator developed in an earlier paper. It also presents a new digital redesign technique, based on matching all the states at all the sampling instants, for finding the pseudo-continuous-time quadratic regulator.

  13. Whole-brain perfusion imaging with balanced steady-state free precession arterial spin labeling.

    PubMed

    Han, Paul Kyu; Ye, Jong Chul; Kim, Eung Yeop; Choi, Seung Hong; Park, Sung-Hong

    2016-03-01

    Recently, balanced steady-state free precession (bSSFP) readout has been proposed for arterial spin labeling (ASL) perfusion imaging to reduce susceptibility artifacts at a relatively high spatial resolution and signal-to-noise ratio (SNR). However, the main limitation of bSSFP-ASL is the low spatial coverage. In this work, methods to increase the spatial coverage of bSSFP-ASL are proposed for distortion-free, high-resolution, whole-brain perfusion imaging. Three strategies of (i) segmentation, (ii) compressed sensing (CS) and (iii) a hybrid approach combining the two methods were tested to increase the spatial coverage of pseudo-continuous ASL (pCASL) with three-dimensional bSSFP readout. The spatial coverage was increased by factors of two, four and six using each of the three approaches, whilst maintaining the same total scan time (5.3 min). The number of segments and/or CS acceleration rate (R) correspondingly increased to maintain the same bSSFP readout time (1.2 s). The segmentation approach allowed whole-brain perfusion imaging for pCASL-bSSFP with no penalty in SNR and/or total scan time. The CS approach increased the spatial coverage of pCASL-bSSFP whilst maintaining the temporal resolution, with minimal impact on the image quality. The hybrid approach provided compromised effects between the two methods. Balanced SSFP-based ASL allows the acquisition of perfusion images with wide spatial coverage, high spatial resolution and SNR, and reduced susceptibility artifacts, and thus may become a good choice for clinical and neurological studies. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26676386

  14. Arterial Spin Labeling Imaging for the Parotid Glands of Patients with Sjögren's Syndrome.

    PubMed

    Kami, Yukiko N; Sumi, Misa; Takagi, Yukinori; Sasaki, Miho; Uetani, Masataka; Nakamura, Takashi

    2016-01-01

    Sjögren's syndrome (SS) is characterized by hypofunction of the salivary and lacrimal glands. The salivary function is largely dependent upon the blood supply in the glands. However, the diseased states of the gland perfusion are not well understood. The arterial spin labeling (ASL) technique allows noninvasive quantitative assessment of tissue perfusion without the need for contrast agent. Here, we prospectively compared the perfusion properties of the parotid glands between patients with SS and those with healthy glands using ASL MR imaging. We analyzed salivary blood flow (SBF) kinetics of 22 healthy parotid glands from 11 volunteers and 28 parotid glands from 14 SS patients using 3T pseudo-continuous ASL imaging. SBF was determined in resting state (base SBF) and at 3 sequential segments after gustatory stimulation. SBF kinetic profiles were characterized by base SBF level, increment ratio at the SBF peak, and the differences in segments where the peak appeared (SBF types). Base SBFs of the SS glands were significantly higher than those of healthy glands (59.2 ± 22.8 vs. 46.3 ± 9.0 mL/min/100 g, p = 0.01). SBF kinetic profiles of the SS glands also exhibited significantly later SBF peaks (p < 0.001) and higher SBF increment ratios (74 ± 49% vs. 47 ± 39%, p = 0.04) than the healthy glands. The best SBF criterion (= 51.2 mL/min/100 mg) differentiated between control subjects and SS patients with 71% sensitivity and 82% specificity. Taken together, these results showed that the SS parotid glands were mostly hyperemic and the SS gland responses to gustatory stimulation were stronger and more prolonged than those of the healthy glands. The ASL may be a promising technique for assessing the diseased salivary gland vascularization of SS patients. PMID:26959680

  15. Whole-brain perfusion imaging with balanced steady-state free precession arterial spin labeling.

    PubMed

    Han, Paul Kyu; Ye, Jong Chul; Kim, Eung Yeop; Choi, Seung Hong; Park, Sung-Hong

    2016-03-01

    Recently, balanced steady-state free precession (bSSFP) readout has been proposed for arterial spin labeling (ASL) perfusion imaging to reduce susceptibility artifacts at a relatively high spatial resolution and signal-to-noise ratio (SNR). However, the main limitation of bSSFP-ASL is the low spatial coverage. In this work, methods to increase the spatial coverage of bSSFP-ASL are proposed for distortion-free, high-resolution, whole-brain perfusion imaging. Three strategies of (i) segmentation, (ii) compressed sensing (CS) and (iii) a hybrid approach combining the two methods were tested to increase the spatial coverage of pseudo-continuous ASL (pCASL) with three-dimensional bSSFP readout. The spatial coverage was increased by factors of two, four and six using each of the three approaches, whilst maintaining the same total scan time (5.3 min). The number of segments and/or CS acceleration rate (R) correspondingly increased to maintain the same bSSFP readout time (1.2 s). The segmentation approach allowed whole-brain perfusion imaging for pCASL-bSSFP with no penalty in SNR and/or total scan time. The CS approach increased the spatial coverage of pCASL-bSSFP whilst maintaining the temporal resolution, with minimal impact on the image quality. The hybrid approach provided compromised effects between the two methods. Balanced SSFP-based ASL allows the acquisition of perfusion images with wide spatial coverage, high spatial resolution and SNR, and reduced susceptibility artifacts, and thus may become a good choice for clinical and neurological studies. Copyright © 2015 John Wiley & Sons, Ltd.

  16. Noise Reduction in Arterial Spin Labeling Based Functional Connectivity Using Nuisance Variables

    PubMed Central

    Jann, Kay; Smith, Robert X.; Rios Piedra, Edgar A.; Dapretto, Mirella; Wang, Danny J. J.

    2016-01-01

    Arterial Spin Labeling (ASL) perfusion image series have recently been utilized for functional connectivity (FC) analysis in healthy volunteers and children with autism spectrum disorders (ASD). Noise reduction by using nuisance variables has been shown to be necessary to minimize potential confounding effects of head motion and physiological signals on BOLD based FC analysis. The purpose of the present study is to systematically evaluate the effectiveness of different noise reduction strategies (NRS) using nuisance variables to improve perfusion based FC analysis in two cohorts of healthy adults using state of the art 3D background-suppressed (BS) GRASE pseudo-continuous ASL (pCASL) and dual-echo 2D-EPI pCASL sequences. Five different NRS were performed in healthy volunteers to compare their performance. We then compared seed-based FC analysis using 3D BS GRASE pCASL in a cohort of 12 children with ASD (3f/9m, age 12.8 ± 1.3 years) and 13 typically developing (TD) children (1f/12m; age 13.9 ± 3 years) in conjunction with NRS. Regression of different combinations of nuisance variables affected FC analysis from a seed in the posterior cingulate cortex (PCC) to other areas of the default mode network (DMN) in both BOLD and pCASL data sets. Consistent with existing literature on BOLD-FC, we observed improved spatial specificity after physiological noise reduction and improved long-range connectivity using head movement related regressors. Furthermore, 3D BS GRASE pCASL shows much higher temporal SNR compared to dual-echo 2D-EPI pCASL and similar effects of noise reduction as those observed for BOLD. Seed-based FC analysis using 3D BS GRASE pCASL in children with ASD and TD children showed that noise reduction including physiological and motion related signals as nuisance variables is crucial for identifying altered long-range connectivity from PCC to frontal brain areas associated with ASD. This is the first study that systematically evaluated the effects of

  17. Noise Reduction in Arterial Spin Labeling Based Functional Connectivity Using Nuisance Variables

    PubMed Central

    Jann, Kay; Smith, Robert X.; Rios Piedra, Edgar A.; Dapretto, Mirella; Wang, Danny J. J.

    2016-01-01

    Arterial Spin Labeling (ASL) perfusion image series have recently been utilized for functional connectivity (FC) analysis in healthy volunteers and children with autism spectrum disorders (ASD). Noise reduction by using nuisance variables has been shown to be necessary to minimize potential confounding effects of head motion and physiological signals on BOLD based FC analysis. The purpose of the present study is to systematically evaluate the effectiveness of different noise reduction strategies (NRS) using nuisance variables to improve perfusion based FC analysis in two cohorts of healthy adults using state of the art 3D background-suppressed (BS) GRASE pseudo-continuous ASL (pCASL) and dual-echo 2D-EPI pCASL sequences. Five different NRS were performed in healthy volunteers to compare their performance. We then compared seed-based FC analysis using 3D BS GRASE pCASL in a cohort of 12 children with ASD (3f/9m, age 12.8 ± 1.3 years) and 13 typically developing (TD) children (1f/12m; age 13.9 ± 3 years) in conjunction with NRS. Regression of different combinations of nuisance variables affected FC analysis from a seed in the posterior cingulate cortex (PCC) to other areas of the default mode network (DMN) in both BOLD and pCASL data sets. Consistent with existing literature on BOLD-FC, we observed improved spatial specificity after physiological noise reduction and improved long-range connectivity using head movement related regressors. Furthermore, 3D BS GRASE pCASL shows much higher temporal SNR compared to dual-echo 2D-EPI pCASL and similar effects of noise reduction as those observed for BOLD. Seed-based FC analysis using 3D BS GRASE pCASL in children with ASD and TD children showed that noise reduction including physiological and motion related signals as nuisance variables is crucial for identifying altered long-range connectivity from PCC to frontal brain areas associated with ASD. This is the first study that systematically evaluated the effects of

  18. Cerebrovascular Reactivity Measured with Arterial Spin Labeling and Blood Oxygen Level Dependent Techniques

    PubMed Central

    Zhou, Yongxia; Rodgers, Zachary B.; Kuo, Anderson H.

    2015-01-01

    Purpose To compare cerebrovascular reactivity (CVR) quantified with pseudo-continuous arterial spin labeling (pCASL) and blood oxygen level dependent (BOLD) fMRI techniques. Materials and Methods Sixteen healthy volunteers (age: 37.8±14.3 years; 6 women and 10 men; education attainment: 17+2.1 years) were recruited and completed a 5% CO2 gas-mixture breathing paradigm at 3T field strength. ASL and BOLD images were acquired for CVR determination assuming that mild hypercapnia does not affect the cerebral metabolic rate of oxygen. Both CVR quantifications were derived as the ratio of the fractional cerebral blood flow (CBF) or BOLD signal change over the change in end-tidal CO2 pressure. Results The absolute CBF, BOLD and CVR measures were consistent with literature values. CBF derived CVR was 5.11 ± 0.87%/mmHg in gray matter (GM) and 4.64 ± 0.37%/mmHg in parenchyma. BOLD CVR was 0.23±0.04 %/mmHg and 0.22±0.04 %/mmHg for GM and parenchyma respectively. The most significant correlations between BOLD and CBF-based CVRs were also in GM structures, with greater vascular response in occipital cortex than in frontal and parietal lobes (6.8 %/mmHg versus 4.5 %/mmHg, 50% greater). Parenchymal BOLD CVR correlated significantly with the fractional change in CBF in response to hypercapnia (r=0.61, P=0.01), suggesting the BOLD response to be significantly flow driven. GM CBF decreased with age in room air (-5.58 mL/100g/min per decade for GM; r=-0.51, P=0.05), but there was no association of CBF with age during hypercapnia. A trend toward increased pCASL CVR with age was observed, scaling as 0.64 %/mmHg per decade for GM. Conclusion Consistent with previously reported CVR values, our results suggest that BOLD and CBF CVR techniques are complementary to each other in evaluating neuronal and vascular underpinning of hemodynamic processes. PMID:25708263

  19. Noise Reduction in Arterial Spin Labeling Based Functional Connectivity Using Nuisance Variables.

    PubMed

    Jann, Kay; Smith, Robert X; Rios Piedra, Edgar A; Dapretto, Mirella; Wang, Danny J J

    2016-01-01

    Arterial Spin Labeling (ASL) perfusion image series have recently been utilized for functional connectivity (FC) analysis in healthy volunteers and children with autism spectrum disorders (ASD). Noise reduction by using nuisance variables has been shown to be necessary to minimize potential confounding effects of head motion and physiological signals on BOLD based FC analysis. The purpose of the present study is to systematically evaluate the effectiveness of different noise reduction strategies (NRS) using nuisance variables to improve perfusion based FC analysis in two cohorts of healthy adults using state of the art 3D background-suppressed (BS) GRASE pseudo-continuous ASL (pCASL) and dual-echo 2D-EPI pCASL sequences. Five different NRS were performed in healthy volunteers to compare their performance. We then compared seed-based FC analysis using 3D BS GRASE pCASL in a cohort of 12 children with ASD (3f/9m, age 12.8 ± 1.3 years) and 13 typically developing (TD) children (1f/12m; age 13.9 ± 3 years) in conjunction with NRS. Regression of different combinations of nuisance variables affected FC analysis from a seed in the posterior cingulate cortex (PCC) to other areas of the default mode network (DMN) in both BOLD and pCASL data sets. Consistent with existing literature on BOLD-FC, we observed improved spatial specificity after physiological noise reduction and improved long-range connectivity using head movement related regressors. Furthermore, 3D BS GRASE pCASL shows much higher temporal SNR compared to dual-echo 2D-EPI pCASL and similar effects of noise reduction as those observed for BOLD. Seed-based FC analysis using 3D BS GRASE pCASL in children with ASD and TD children showed that noise reduction including physiological and motion related signals as nuisance variables is crucial for identifying altered long-range connectivity from PCC to frontal brain areas associated with ASD. This is the first study that systematically evaluated the effects of

  20. Evaluation of segmented 3D acquisition schemes for whole-brain high-resolution arterial spin labeling at 3 T.

    PubMed

    Vidorreta, Marta; Balteau, Evelyne; Wang, Ze; De Vita, Enrico; Pastor, María A; Thomas, David L; Detre, John A; Fernández-Seara, María A

    2014-11-01

    Recent technical developments have significantly increased the signal-to-noise ratio (SNR) of arterial spin labeled (ASL) perfusion MRI. Despite this, typical ASL acquisitions still employ large voxel sizes. The purpose of this work was to implement and evaluate two ASL sequences optimized for whole-brain high-resolution perfusion imaging, combining pseudo-continuous ASL (pCASL), background suppression (BS) and 3D segmented readouts, with different in-plane k-space trajectories. Identical labeling and BS pulses were implemented for both sequences. Two segmented 3D readout schemes with different in-plane trajectories were compared: Cartesian (3D GRASE) and spiral (3D RARE Stack-Of-Spirals). High-resolution perfusion images (2 × 2 × 4 mm(3) ) were acquired in 15 young healthy volunteers with the two ASL sequences at 3 T. The quality of the perfusion maps was evaluated in terms of SNR and gray-to-white matter contrast. Point-spread-function simulations were carried out to assess the impact of readout differences on the effective resolution. The combination of pCASL, in-plane segmented 3D readouts and BS provided high-SNR high-resolution ASL perfusion images of the whole brain. Although both sequences produced excellent image quality, the 3D RARE Stack-Of-Spirals readout yielded higher temporal and spatial SNR than 3D GRASE (spatial SNR = 8.5 ± 2.8 and 3.7 ± 1.4; temporal SNR = 27.4 ± 12.5 and 15.6 ± 7.6, respectively) and decreased through-plane blurring due to its inherent oversampling of the central k-space region, its reduced effective TE and shorter total readout time, at the expense of a slight increase in the effective in-plane voxel size. PMID:25263944

  1. Arterial Spin Labeling Imaging for the Parotid Glands of Patients with Sjögren’s Syndrome

    PubMed Central

    Kami, Yukiko N.; Sumi, Misa; Takagi, Yukinori; Sasaki, Miho; Uetani, Masataka; Nakamura, Takashi

    2016-01-01

    Sjögren’s syndrome (SS) is characterized by hypofunction of the salivary and lacrimal glands. The salivary function is largely dependent upon the blood supply in the glands. However, the diseased states of the gland perfusion are not well understood. The arterial spin labeling (ASL) technique allows noninvasive quantitative assessment of tissue perfusion without the need for contrast agent. Here, we prospectively compared the perfusion properties of the parotid glands between patients with SS and those with healthy glands using ASL MR imaging. We analyzed salivary blood flow (SBF) kinetics of 22 healthy parotid glands from 11 volunteers and 28 parotid glands from 14 SS patients using 3T pseudo-continuous ASL imaging. SBF was determined in resting state (base SBF) and at 3 sequential segments after gustatory stimulation. SBF kinetic profiles were characterized by base SBF level, increment ratio at the SBF peak, and the differences in segments where the peak appeared (SBF types). Base SBFs of the SS glands were significantly higher than those of healthy glands (59.2 ± 22.8 vs. 46.3 ± 9.0 mL/min/100 g, p = 0.01). SBF kinetic profiles of the SS glands also exhibited significantly later SBF peaks (p < 0.001) and higher SBF increment ratios (74 ± 49% vs. 47 ± 39%, p = 0.04) than the healthy glands. The best SBF criterion (= 51.2 mL/min/100 mg) differentiated between control subjects and SS patients with 71% sensitivity and 82% specificity. Taken together, these results showed that the SS parotid glands were mostly hyperemic and the SS gland responses to gustatory stimulation were stronger and more prolonged than those of the healthy glands. The ASL may be a promising technique for assessing the diseased salivary gland vascularization of SS patients. PMID:26959680

  2. Impact of pseudo-continuous fermentation on the ethanol tolerance of Scheffersomyces stipitis.

    PubMed

    Liang, Meng; Kim, Min Hea; He, Qinghua Peter; Wang, Jin

    2013-09-01

    In this work we conducted the pseudo-continuous fermentation, i.e., continuous fermentation with cell retention, using Scheffersomyces stipitis, and studied its effect on ethanol tolerance of the strain. During the fermentation experiments, S. stipitis was adapted to a mild concentration of ethanol (20-26 g/L) for two weeks. Two substrates (glucose and xylose) were used in different fermentation experiments. After fermentation, various experiments were performed to evaluate the ethanol tolerance of adapted cells and unadapted cells. Compared to the unadapted cells, the viability of adapted cells increased by 8 folds with glucose as the carbon source and 6 folds with xylose as the carbon source following exposure to 60 g/L ethanol for 2 h. Improved ethanol tolerance of the adapted cells was also revealed in the effects of ethanol on plasma membrane permeability, extracellular alkalization and acidification. The mathematical modeling of cell leakage, extracellular alkalization and acidification revealed that cells cultured on glucose show better ethanol tolerance than cells cultured on xylose but the differences become smaller for adapted cells. The results show that pseudo-continuous fermentation can effectively improve cell's ethanol tolerance due to the environmental pressure during the fermentation process.

  3. Applications of arterial spin labeled MRI in the brain.

    PubMed

    Detre, John A; Rao, Hengyi; Wang, Danny J J; Chen, Yu Fen; Wang, Ze

    2012-05-01

    Perfusion provides oxygen and nutrients to tissues and is closely tied to tissue function while disorders of perfusion are major sources of medical morbidity and mortality. It has been almost two decades since the use of arterial spin labeling (ASL) for noninvasive perfusion imaging was first reported. While initial ASL magnetic resonance imaging (MRI) studies focused primarily on technological development and validation, a number of robust ASL implementations have emerged, and ASL MRI is now also available commercially on several platforms. As a result, basic science and clinical applications of ASL MRI have begun to proliferate. Although ASL MRI can be carried out in any organ, most studies to date have focused on the brain. This review covers selected research and clinical applications of ASL MRI in the brain to illustrate its potential in both neuroscience research and clinical care.

  4. Using arterial spin labeling to examine mood states in youth

    PubMed Central

    Mikita, Nina; Mehta, Mitul A; Zelaya, Fernando O; Stringaris, Argyris

    2015-01-01

    Introduction Little is known about the neural correlates of mood states and the specific physiological changes associated with their valence and duration, especially in young people. Arterial spin labeling (ASL) imaging is particularly well-suited to study sustained cerebral states in young people, due to its robustness to low-frequency drift, excellent interscan reliability, and noninvasiveness. Yet, it has so far been underutilized for understanding the neural mechanisms underlying mood states in youth. Methods In this exploratory study, 21 healthy adolescents aged 16 to 18 took part in a mood induction experiment. Neutral, sad, and happy mood states were induced using film clips and explicit instructions. An ASL scan was obtained following presentation of each film clip. Results Mood induction led to robust changes in self-reported mood ratings. Compared to neutral, sad mood was associated with increased regional cerebral blood flow (rCBF) in the left middle frontal gyrus and anterior prefrontal cortex, and decreased rCBF in the right middle frontal gyrus and the inferior parietal lobule. A decrease in self-reported mood from neutral to sad condition was associated with increased rCBF in the precuneus. Happy mood was associated with increased rCBF in medial frontal and cingulate gyri, the subgenual anterior cingulate cortex, and ventral striatum, and decreased rCBF in the inferior parietal lobule. The level of current self-reported depressive symptoms was negatively associated with rCBF change in the cerebellum and lingual gyrus following both sad and happy mood inductions. Conclusions Arterial spin labeling is sensitive to experimentally induced mood changes in healthy young people. The effects of happy mood on rCBF patterns were generally stronger than the effects of sad mood. PMID:26085964

  5. Bolus-tracking arterial spin labelling: theoretical and experimental results

    NASA Astrophysics Data System (ADS)

    Kelly, M. E.; Blau, C. W.; Kerskens, C. M.

    2009-03-01

    Arterial spin labelling (ASL) is a magnetic resonance imaging (MRI) technique that can be used to provide a quantitative assessment of cerebral perfusion. Despite the development of a number of theoretical models to facilitate quantitative ASL, some key challenges still remain. The purpose of this study is to develop a novel quantitative ASL method based on a macroscopic model that reduces the number of variables required to describe the physiological processes involved. To this end, a novel Fokker-Planck equation consisting of stochastically varying macroscopic variables was derived from a general Langevin equation. ASL data from the rat brain was acquired using a bolus-tracking ASL protocol where a bolus of labelled spins flowing from an inversion plane in the neck into an imaging plane in the brain can be observed. Bolus durations of 1.5 s, 2.0 s and 3.0 s were used and the solution to the Fokker-Planck equation for the boundary conditions of bolus-tracking ASL was fitted to the experimental data using a least-squares fit. The mean transit time (MTT) and capillary transit time (CTT) were calculated from the first and second moments of the resultant curve respectively and the arterial transit time (ATT) was calculated by subtracting the CTT from the MTT. The average MTT, CTT and ATT values were 1.75 ± 0.22 s, 1.43 ± 0.12 s and 0.32 ± 0.04 s respectively. In conclusion, a new ASL protocol has been developed by combining the theoretical model with ASL experiments. The technique has the unique ability to provide solutions for varying bolus volumes and the generality of the new model is demonstrated by the derivation of additional solutions for the continuous and pulsed ASL (CASL and PASL) techniques.

  6. Improving arterial spin labeling data by temporal filtering

    NASA Astrophysics Data System (ADS)

    Petr, Jan; Ferre, Jean-Christophe; Gauvrit, Jean-Yves; Barillot, Christian

    2010-03-01

    Arterial spin labeling (ASL) is an MRI method for imaging brain perfusion by magnetically labeling blood in brain feeding arteries. The perfusion is obtained from the difference between images with and without prior labeling. Image noise is one of the main problems of ASL as the difference is around 0.5-2% of the image magnitude. Usually, 20-40 pairs of images need to be acquired and averaged to reach a satisfactory quality. The images are acquired shortly after the labeling to allow the labeled blood to reach the imaged slice. A sequence of images with multiple delays is more suitable for quantification of the cerebral blood flow as it gives more information about the blood arrival and relaxation. Although the quantification methods are sensitive to noise, no filtering or only Gaussian filtering is used to denoise the data in the temporal domain prior to quantification. In this article, we propose an efficient way to use the redundancy of information in the time sequence of each pixel to suppress noise. For this purpose, the vectorial NL-means method is adapted to work in the temporal domain. The proposed method is tested on simulated and real 3T MRI data. We demonstrate a clear improvement of the image quality as well as a better performance compared to Gaussian and normal spatial NL-means filtering.

  7. Pseudocontinuous arterial spin labeling with optimized tagging efficiency.

    PubMed

    Shin, David D; Liu, Thomas T; Wong, Eric C; Shankaranarayanan, Ajit; Jung, Youngkyoo

    2012-10-01

    The adiabatic inversion of blood in pseudocontinuous arterial spin labeling (PCASL) is highly sensitive to off-resonance effects and gradient imperfections and this sensitivity can lead to tagging efficiency loss and unpredictable variations in cerebral blood flow estimates. This efficiency loss is caused by a phase tracking error between the RF pulses and the flowing spins. This article introduces a new method, referred to as Optimized PCASL (OptPCASL), that minimizes the phase tracking error by applying an additional compensation RF phase term and in-plane gradients to the PCASL pulse train. The optimal RF phase and gradient amplitudes are determined using a prescan procedure, which consists of a series of short scans interleaved with automated postprocessing routines integrated to the scanner console. The prescan procedure is shown to minimize the phase tracking error in a robust and time efficient manner. As an example of its application, the use of OptPCASL for the improved detection of functional activation in the visual cortex is demonstrated and temporal signal-to-noise ratio (SNR), image SNR, and baseline cerebral blood flow measures are compared to those acquired from conventional PCASL. PMID:22234782

  8. Volumetric Measurement of Perfusion and Arterial Transit Delay using Hadamard Encoded Continuous Arterial Spin Labeling

    PubMed Central

    Dai, Weiying; Shankaranarayanan, Ajit; Alsop, David C.

    2012-01-01

    Creating images of the transit delay from the labeling location to image tissue can aid the optimization and quantification of arterial spin labeling (ASL) perfusion measurements and may provide diagnostic information independent of perfusion. Unfortunately, measuring transit delay requires acquiring a series of images with different labeling timing that adds to the time cost and increases the noise of the ASL study. Here we implement and evaluate a proposed Hadamard encoding of labeling that speeds the imaging and improves the signal-to-noise ratio (SNR) efficiency. Volumetric images in human volunteers confirmed the theoretical advantages of Hadamard encoding over sequential acquisition of images with multiple labeling timing. Perfusion images calculated from Hadamard encoded acquisition had reduced SNR relative to a dedicated perfusion acquisition with either assumed or separately measured transit delays, however. PMID:22618894

  9. Diagnostic Potential of Pulsed Arterial Spin Labeling in Alzheimer's Disease

    PubMed Central

    Trebeschi, Stefano; Riederer, Isabelle; Preibisch, Christine; Bohn, Karl P.; Förster, Stefan; Alexopoulos, Panagiotis; Zimmer, Claus; Kirschke, Jan S.; Valentinitsch, Alexander

    2016-01-01

    Alzheimers disease (AD) is the most common cause of dementia. Although the underlying pathology is still not completely understood, several diagnostic methods are available. Frequently, the most accurate methods are also the most invasive. The present work investigates the diagnostic potential of Pulsed Arterial Spin Labeling (PASL) for AD: a non-invasive, MRI-based technique for the quantification of regional cerebral blood flow (rCBF). In particular, we propose a pilot computer aided diagnostic (CAD) procedure able to discriminate between healthy and diseased subjects, and at the same time, providing visual informative results. This method encompasses the creation of a healthy model, the computation of a voxel-wise likelihood function as comparison between the healthy model and the subject under examination, and the correction of the likelihood function via prior distributions. The discriminant analysis is carried out to maximize the accuracy of the classification. The algorithm has been trained on a dataset of 81 subjects and achieved a sensitivity of 0.750 and a specificity of 0.875. Moreover, in accordance with the current pathological knowledge, the parietal lobe, and limbic system are shown to be the main discriminant factors. PMID:27147946

  10. Characterizing Resting-State Brain Function Using Arterial Spin Labeling.

    PubMed

    Chen, J Jean; Jann, Kay; Wang, Danny J J

    2015-11-01

    Arterial spin labeling (ASL) is an increasingly established magnetic resonance imaging (MRI) technique that is finding broader applications in studying the healthy and diseased brain. This review addresses the use of ASL to assess brain function in the resting state. Following a brief technical description, we discuss the use of ASL in the following main categories: (1) resting-state functional connectivity (FC) measurement: the use of ASL-based cerebral blood flow (CBF) measurements as an alternative to the blood oxygen level-dependent (BOLD) technique to assess resting-state FC; (2) the link between network CBF and FC measurements: the use of network CBF as a surrogate of the metabolic activity within corresponding networks; and (3) the study of resting-state dynamic CBF-BOLD coupling and cerebral metabolism: the use of dynamic CBF information obtained using ASL to assess dynamic CBF-BOLD coupling and oxidative metabolism in the resting state. In addition, we summarize some future challenges and interesting research directions for ASL, including slice-accelerated (multiband) imaging as well as the effects of motion and other physiological confounds on perfusion-based FC measurement. In summary, this work reviews the state-of-the-art of ASL and establishes it as an increasingly viable MRI technique with high translational value in studying resting-state brain function.

  11. Assessing Reperfusion With Whole-Brain Arterial Spin Labeling

    PubMed Central

    Mirasol, Raymond V.; Bokkers, Reinoud P.H.; Hernandez, Daymara A.; Merino, José G.; Luby, Marie; Warach, Steven; Latour, Lawrence L.

    2014-01-01

    Background and Purpose Arterial spin labeling (ASL) is a perfusion imaging technique that does not require gadolinium. The study aimed to assess the reliability of ASL for evaluating reperfusion in acute ischemic stroke in comparison with dynamic susceptibility contrast (DSC) imaging. Methods The study included 24 patients with acute ischemic stroke on admission and 24-hour follow-up ASL and DSC scans. Two readers rated images for interpretability and evidence of reperfusion. Cohen unweighted κ was used to assess (1) inter-rater reliability between readers for determining interpretability and the presence of reperfusion, (2) agreement between ASL and DSC for determining reperfusion for individual raters, and (3) agreement between ASL and DSC for determining reperfusion after consensus. Results Inter-rater reliability for both ASL and DSC was moderate to good (κ of 0.67 versus 0.55, respectively). Reader 1 rated 16 patients as having interpretable ASL and DSC when compared with 15 patients for reader 2. The κ between ASL and DSC for determining reperfusion was 0.50 for reader 1 and 0.595 for reader 2. After consensus, 18 ASL and 17 DSC image sets were rated interpretable for reperfusion and 13 had both interpretable ASL and DSC scans, yielding a κ for assessment of reperfusion of 0.8. Conclusions Inter-rater reliability of ASL and DSC was moderate to good. Agreement between ASL and DSC for determining reperfusion was moderate for each individual rater and increased substantially after consensus. ASL is a noninvasive and practical alternative to DSC for reperfusion assessments in patients with confirmed acute ischemic stroke. PMID:24385278

  12. Arterial spin labelling reveals prolonged arterial arrival time in idiopathic Parkinson's disease

    PubMed Central

    Al-Bachari, Sarah; Parkes, Laura M.; Vidyasagar, Rishma; Hanby, Martha F.; Tharaken, Vivek; Leroi, Iracema; Emsley, Hedley C.A.

    2014-01-01

    Idiopathic Parkinson's disease (IPD) is the second most common neurodegenerative disease, yet effective disease modifying treatments are still lacking. Neurodegeneration involves multiple interacting pathological pathways. The extent to which neurovascular mechanisms are involved is not well defined in IPD. We aimed to determine whether novel magnetic resonance imaging (MRI) techniques, including arterial spin labelling (ASL) quantification of cerebral perfusion, can reveal altered neurovascular status (NVS) in IPD. Fourteen participants with IPD (mean ± SD age 65.1 ± 5.9 years) and 14 age and cardiovascular risk factor matched control participants (mean ± SD age 64.6 ± 4.2 years) underwent a 3T MRI scan protocol. ASL images were collected before, during and after a 6 minute hypercapnic challenge. FLAIR images were used to determine white matter lesion score. Quantitative images of cerebral blood flow (CBF) and arterial arrival time (AAT) were calculated from the ASL data both at rest and during hypercapnia. Cerebrovascular reactivity (CVR) images were calculated, depicting the change in CBF and AAT relative to the change in end-tidal CO2. A significant (p = 0.005) increase in whole brain averaged baseline AAT was observed in IPD participants (mean ± SD age 1532 ± 138 ms) compared to controls (mean ± SD age 1335 ± 165 ms). Voxel-wise analysis revealed this to be widespread across the brain. However, there were no statistically significant differences in white matter lesion score, CBF, or CVR between patients and controls. Regional CBF, but not AAT, in the IPD group was found to correlate positively with Montreal cognitive assessment (MoCA) scores. These findings provide further evidence of alterations in NVS in IPD. PMID:25379411

  13. Arterial spin labeling imaging reveals widespread and Aβ-independent reductions in cerebral blood flow in elderly apolipoprotein epsilon-4 carriers.

    PubMed

    Michels, Lars; Warnock, Geoffrey; Buck, Alfred; Macauda, Gianluca; Leh, Sandra E; Kaelin, Andrea M; Riese, Florian; Meyer, Rafael; O'Gorman, Ruth; Hock, Christoph; Kollias, Spyros; Gietl, Anton F

    2016-03-01

    Changes in cerebral blood flow are an essential feature of Alzheimer's disease and have been linked to apolipoprotein E-genotype and cerebral amyloid-deposition. These factors could be interdependent or influence cerebral blood flow via different mechanisms. We examined apolipoprotein E-genotype, amyloid beta-deposition, and cerebral blood flow in amnestic mild cognitive impairment using pseudo-continuous arterial spin labeling MRI in 27 cognitively normal elderly and 16 amnestic mild cognitive impairment participants. Subjects underwent Pittsburgh Compound B (PiB) positron emission tomography and apolipoprotein E-genotyping. Global cerebral blood flow was lower in apolipoprotein E ɛ4-allele carriers (apolipoprotein E4+) than in apolipoprotein E4- across all subjects (including cognitively normal participants) and within the group of cognitively normal elderly. Global cerebral blood flow was lower in subjects with mild cognitive impairment compared with cognitively normal. Subjects with elevated cerebral amyloid-deposition (PiB+) showed a trend for lower global cerebral blood flow. Apolipoprotein E-status exerted the strongest effect on global cerebral blood flow. Regional analysis indicated that local cerebral blood flow reductions were more widespread for the contrasts apolipoprotein E4+ versus apolipoprotein E4- compared with the contrasts PiB+ versus PiB- or mild cognitive impairment versus cognitively normal. These findings suggest that apolipoprotein E-genotype exerts its impact on cerebral blood flow at least partly independently from amyloid beta-deposition, suggesting that apolipoprotein E also contributes to cerebral blood flow changes outside the context of Alzheimer's disease.

  14. Arterial Spin Labeling Measurements of Cerebral Perfusion Territories in Experimental Ischemic Stroke

    PubMed Central

    Leoni, Renata F.; Paiva, Fernando F.; Kang, Byeong-Teck; Henning, Erica C.; Nascimento, George C.; Tannús, Alberto; De Araújo, Dráulio B.; Silva, Afonso C.

    2016-01-01

    Collateral circulation, defined as the supplementary vascular network that maintains cerebral blood flow (CBF) when the main vessels fail, constitutes one important defense mechanism of the brain against ischemic stroke. In the present study, continuous arterial spin labeling (CASL) was used to quantify CBF and obtain perfusion territory maps of the major cerebral arteries in spontaneously hypertensive rats (SHR) and their normotensive Wistar-Kyoto (WKY) controls. Results show that both WKY and SHR have complementary, yet significantly asymmetric perfusion territories. Right or left dominances were observed in territories of the anterior (ACA), middle and posterior cerebral arteries, and the thalamic artery. Magnetic resonance angiography showed that some of the asymmetries were correlated with variations of the ACA. The leptomeningeal circulation perfusing the outer layers of the cortex was observed as well. Significant and permanent changes in perfusion territories were obtained after temporary occlusion of the right middle cerebral artery in both SHR and WKY, regardless of their particular dominance. However, animals with right dominance presented a larger volume change of the left perfusion territory (23 ± 9%) than animals with left dominance (7 ± 5%, P < 0.002). The data suggest that animals with contralesional dominance primarily safeguard local CBF values with small changes in contralesional perfusion territory, while animals with ipsilesional dominance show a reversal of dominance and a substantial increase in contralesional perfusion territory. These findings show the usefulness of CASL to probe the collateral circulation. PMID:24323754

  15. Two analytical solutions for a model of pulsed arterial spin labeling with randomized blood arrival times

    NASA Astrophysics Data System (ADS)

    Hrabe, J.; Lewis, D. P.

    2004-03-01

    A fairly general theoretical model for pulsed arterial spin labeling perfusion methods has been available for some time but analytical solutions were derived for only a small number of arterial blood input functions. These mostly assumed a sudden and simultaneous arrival of the tagged blood into the imaged region. More general cases had to be handled numerically. We present analytical solutions for two more realistic arterial input functions. They both allow the arrival times of the molecules of tagged arterial blood to be statistically distributed. We consider cases of (1) a uniform distribution on a finite time interval and (2) a normal distribution characterized by its mean and standard deviation. These models are physiologically meaningful because the statistical nature of the arrival times reflects the distribution of velocities and path lengths that the blood water molecules undertake from the tagging region to the imaged region. The model parameters can be estimated from the measured dependency of the perfusion signal on the tag inversion time.

  16. Implementation of quantitative perfusion imaging techniques for functional brain mapping using pulsed arterial spin labeling.

    PubMed

    Wong, E C; Buxton, R B; Frank, L R

    1997-01-01

    We describe here experimental considerations in the implementation of quantitative perfusion imaging techniques for functional MRI using pulsed arterial spin labeling. Three tagging techniques: EPISTAR, PICORE, and FAIR are found to give very similar perfusion results despite large differences in static tissue contrast. Two major sources of systematic error in the perfusion measurement are identified: the transit delay from the tagging region to the imaging slice; and the inclusion of intravascular tagged signal. A modified technique called QUIPSS II is described that decreases sensitivity to these effects by explicitly controlling the time width of the tag bolus and imaging after the bolus is entirely deposited into the slice. With appropriate saturation pulses the pulse sequence can be arranged so as to allow for simultaneous collection of perfusion and BOLD data that can be cleanly separated. Such perfusion and BOLD signals reveal differences in spatial location and dynamics that may be useful both for functional brain mapping and for study of the BOLD contrast mechanism. The implementation of multislice perfusion imaging introduces additional complications, primarily in the elimination of signal from static tissue. In pulsed ASL, this appears to be related to the slice profile of the inversion tag pulse in the presence of relaxation, rather than magnetization transfer effects as in continuous arterial spin labeling, and can be alleviated with careful adjustment of inversion pulse parameters. PMID:9430354

  17. Challenges for non-invasive brain perfusion quantification using arterial spin labeling.

    PubMed

    Sousa, I; Santos, N; Sanches, J; Figueiredo, P

    2011-03-29

    Arterial Spin Labeling (ASL) sequences for perfusion Magnetic Resonance Imaging (MRI) have recently become available to be used in the clinical practice, offering a completely non-invasive technique for the quantitative evaluation of brain perfusion. Despite its great potential, ASL perfusion imaging still presents important methodological challenges before its incorporation in routine protocols. Specifically, in some pathological conditions in which the cerebrovascular dynamics is altered, the standard application of ASL may lead to measurement errors. In these cases, it would be possible to estimate perfusion, as well as arterial transit times, by collecting images at multiple time points and then fitting a mathematical model to the data. This approach can be optimized by selecting a set of optimal imaging time points and incorporating knowledge about the physiological distributions of the parameters into the model estimation procedures. In this study, we address the challenges that arise in the measurement of brain perfusion using PASL, due to variations in the arterial transit times, by estimating the errors produced using different types of acquisitions and proposing methods for minimizing such errors. We show by simulation that multiple inversion time ASL acquisitions are expected to reduce measurement errors relative to standard approaches. In data collected from a group of subjects, we further observed reduced inter-subject variability in perfusion measurements when using a multiple versus single inversion time acquisitions. Both measurement errors and variability were further reduced if optimized acquisition and analysis techniques were employed.

  18. Sickle cell anemia: reference values of cerebral blood flow determined by continuous arterial spin labeling MRI.

    PubMed

    Arkuszewski, M; Krejza, J; Chen, R; Melhem, E R

    2013-04-01

    Sickle cell anemia (SCA) is a chronic illness associated with progressive deterioration in patients' quality of life. The major complications of SCA are cerebrovascular accidents (CVA) such as asymptomatic cerebral infarct or overt stroke. The risk of CVA may be related to chronic disturbances in cerebral blood flow (CBF), but the thresholds of "normal" steady-state CBF are not well established. The reference tolerance limits of CBF can be useful to estimate the risk of CVA in asymptomatic children with SCA, who are negative for hyperemia or evidence of arterial narrowing. Continuous arterial spin labeling (CASL) MR perfusion allows for non-invasive quantification of global and regional CBF. To establish such reference tolerance limits we performed CASL MR examinations on a 3-Tesla MR scanner in a carefully selected cohort of 42 children with SCA (mean age, 8.1±3.3 years; range limits, 2.3-14.4 years; 24 females), who were not on chronic transfusion therapy, had no history of overt stroke or transient ischemic attack, were free of signs and symptoms of focal vascular territory ischemic brain injury, did not have intracranial arterial narrowing on MR angiography and were at low risk for stroke as determined by transcranial Doppler ultrasonography.

  19. Challenges for non-invasive brain perfusion quantification using arterial spin labeling.

    PubMed

    Sousa, I; Santos, N; Sanches, J; Figueiredo, P

    2011-03-29

    Arterial Spin Labeling (ASL) sequences for perfusion Magnetic Resonance Imaging (MRI) have recently become available to be used in the clinical practice, offering a completely non-invasive technique for the quantitative evaluation of brain perfusion. Despite its great potential, ASL perfusion imaging still presents important methodological challenges before its incorporation in routine protocols. Specifically, in some pathological conditions in which the cerebrovascular dynamics is altered, the standard application of ASL may lead to measurement errors. In these cases, it would be possible to estimate perfusion, as well as arterial transit times, by collecting images at multiple time points and then fitting a mathematical model to the data. This approach can be optimized by selecting a set of optimal imaging time points and incorporating knowledge about the physiological distributions of the parameters into the model estimation procedures. In this study, we address the challenges that arise in the measurement of brain perfusion using PASL, due to variations in the arterial transit times, by estimating the errors produced using different types of acquisitions and proposing methods for minimizing such errors. We show by simulation that multiple inversion time ASL acquisitions are expected to reduce measurement errors relative to standard approaches. In data collected from a group of subjects, we further observed reduced inter-subject variability in perfusion measurements when using a multiple versus single inversion time acquisitions. Both measurement errors and variability were further reduced if optimized acquisition and analysis techniques were employed. PMID:24059574

  20. Reduction in Cerebral Perfusion after Heroin Administration: A Resting State Arterial Spin Labeling Study

    PubMed Central

    Denier, Niklaus; Gerber, Hana; Vogel, Marc; Klarhöfer, Markus; Riecher-Rossler, Anita; Wiesbeck, Gerhard A.; Lang, Undine E.; Borgwardt, Stefan; Walter, Marc

    2013-01-01

    Heroin dependence is a chronic relapsing brain disorder, characterized by the compulsion to seek and use heroin. Heroin itself has a strong potential to produce subjective experiences characterized by intense euphoria, relaxation and release from craving. The neurofunctional foundations of these perceived effects are not well known. In this study, we have used pharmacological magnetic resonance imaging (phMRI) in 15 heroin-dependent patients from a stable heroin-assisted treatment program to observe the steady state effects of heroin (60 min after administration). Patients were scanned in a cross-over and placebo controlled design. They received an injection of their regular dose of heroin or saline (placebo) before or after the scan. As phMRI method, we used a pulsed arterial spin labeling (ASL) sequence based on a flow-sensitive alternating inversion recovery (FAIR) spin labeling scheme combined with a single-shot 3D GRASE (gradient-spin echo) readout on a 3 Tesla scanner. Analysis was performed with Statistical Parametric Mapping (SPM 8), using a general linear model for whole brain comparison between the heroin and placebo conditions. We found that compared to placebo, heroin was associated with reduced perfusion in the left anterior cingulate cortex (ACC), the left medial prefrontal cortex (mPFC) and in the insula (both hemispheres). Analysis of extracted perfusion values indicate strong effect sizes and no gender related differences. Reduced perfusion in these brain areas may indicate self- and emotional regulation effects of heroin in maintenance treatment. PMID:24039715

  1. Measurement of vascular water transport in human subjects using time-resolved pulsed arterial spin labelling.

    PubMed

    Bibic, Adnan; Knutsson, Linda; Schmidt, Anders; Henningsson, Erik; Månsson, Sven; Abul-Kasim, Kasim; Åkeson, Jonas; Gunther, Matthias; Ståhlberg, Freddy; Wirestam, Ronnie

    2015-08-01

    Most approaches to arterial spin labelling (ASL) data analysis aim to provide a quantitative measure of the cerebral blood flow (CBF). This study, however, focuses on the measurement of the transfer time of blood water through the capillaries to the parenchyma (referred to as the capillary transfer time, CTT) as an alternative parameter to characterise the haemodynamics of the system. The method employed is based on a non-compartmental model, and no measurements need to be added to a common time-resolved ASL experiment. Brownian motion of labelled spins in a potential was described by a one-dimensional general Langevin equation as the starting point, and as a Fokker-Planck differential equation for the averaged distribution of labelled spins at the end point, which takes into account the effects of flow and dispersion of labelled water by the pseudorandom nature of the microvasculature and the transcapillary permeability. Multi-inversion time (multi-TI) ASL data were acquired in 14 healthy subjects on two occasions in a test-retest design, using a pulsed ASL sequence and three-dimensional gradient and spin echo (3D-GRASE) readout. Based on an error analysis to predict the size of a region of interest (ROI) required to obtain reasonably precise parameter estimates, data were analysed in two relatively large ROIs, i.e. the occipital lobe (OC) and the insular cortex (IC). The average values of CTT in OC were 260 ± 60 ms in the first experiment and 270 ± 60 ms in the second experiment. The corresponding IC values were 460 ± 130 ms and 420 ± 139 ms, respectively. Information related to the water transfer time may be important for diagnostics and follow-up of cerebral conditions or diseases characterised by a disrupted blood-brain barrier or disturbed capillary blood flow.

  2. Comparing model-based and model-free analysis methods for QUASAR arterial spin labeling perfusion quantification.

    PubMed

    Chappell, Michael A; Woolrich, Mark W; Petersen, Esben T; Golay, Xavier; Payne, Stephen J

    2013-05-01

    Amongst the various implementations of arterial spin labeling MRI methods for quantifying cerebral perfusion, the QUASAR method is unique. By using a combination of labeling with and without flow suppression gradients, the QUASAR method offers the separation of macrovascular and tissue signals. This permits local arterial input functions to be defined and "model-free" analysis, using numerical deconvolution, to be used. However, it remains unclear whether arterial spin labeling data are best treated using model-free or model-based analysis. This work provides a critical comparison of these two approaches for QUASAR arterial spin labeling in the healthy brain. An existing two-component (arterial and tissue) model was extended to the mixed flow suppression scheme of QUASAR to provide an optimal model-based analysis. The model-based analysis was extended to incorporate dispersion of the labeled bolus, generally regarded as the major source of discrepancy between the two analysis approaches. Model-free and model-based analyses were compared for perfusion quantification including absolute measurements, uncertainty estimation, and spatial variation in cerebral blood flow estimates. Major sources of discrepancies between model-free and model-based analysis were attributed to the effects of dispersion and the degree to which the two methods can separate macrovascular and tissue signal.

  3. 3D Pseudocontinuous arterial spin labeling in routine clinical practice: A review of clinically significant artifacts.

    PubMed

    Amukotuwa, Shalini A; Yu, Caroline; Zaharchuk, Gregory

    2016-01-01

    Arterial spin labeling (ASL) is a completely noninvasive magnetic resonance imaging (MRI) perfusion method for quantitatively measuring cerebral blood flow utilizing magnetically labeled arterial water. Advances in the technique have enabled the major MRI vendors to make the sequence available to the clinical neuroimaging community. Consequently, ASL is being increasingly incorporated into the routine neuroimaging protocol. Although a variety of ASL techniques are available, the ISMRM Perfusion Study Group and the European ASL in Dementia Consortium have released consensus guidelines recommending standardized implementation of 3D pseudocontinuous ASL with background suppression. The purpose of this review, aimed at the large number of neuroimaging clinicians who have either no or limited experience with this 3D pseudocontinuous ASL, is to discuss the common and clinically significant artifacts that may be encountered with this technique. While some of these artifacts hinder accurate interpretation of studies, either by degrading the images or mimicking pathology, there are other artifacts that are of clinical utility, because they increase the conspicuity of pathology. Cognizance of these artifacts will help the physician interpreting ASL to avoid potential diagnostic pitfalls, and increase their level of comfort with the technique.

  4. Resting quantitative cerebral blood flow in schizophrenia measured by pulsed arterial spin labeling perfusion MRI

    PubMed Central

    Pinkham, Amy; Loughead, James; Ruparel, Kosha; Wu, Wen-Chau; Overton, Eve; Gur, Raquel; Gur, Ruben

    2011-01-01

    Arterial spin labeling imaging (ASL) perfusion MRI is a relatively novel technique that can allow for quantitative measurement of cerebral blood flow (CBF) by using magnetically labeled arterial blood water as an endogenous tracer. Available data on resting CBF in schizophrenia primarily comes from invasive and expensive nuclear medicine techniques that are often limited to small samples and yield mixed results. The noninvasive nature of ASL offers promise for larger-scale studies. The utility of this approach was examined in 24 healthy controls and 30 patients with schizophrenia. Differences between groups in quantitative CBF were assessed, as were relationships between CBF and psychiatric symptoms. Group comparisons demonstrated greater CBF for controls in several regions including bilateral precuneus and middle frontal gyrus. Patients showed increased CBF in left putamen/superior corona radiata and right middle temporal gyrus. For patients, greater severity of negative symptoms was associated with reduced CBF in bilateral superior temporal gyrus, cingulate gyrus, and left middle frontal gyrus. Increased severity of positive symptoms was related to both higher CBF in cingulate gyrus and superior frontal gyrus and decreased CBF in precentral gyrus/middle frontal gyrus. These findings support the feasibility and utility of implementing ASL in schizophrenia research and expand upon previous results. PMID:21831608

  5. Vessel-selective, non-contrast enhanced, time-resolved MR angiography with vessel-selective arterial spin labeling technique (CINEMA-SELECT) in intracranial arteries.

    PubMed

    Nakamura, Masanobu; Yoneyama, Masami; Tabuchi, Takashi; Takemura, Atsushi; Obara, Makoto; Tatsuno, Satoshi; Sawano, Seishi

    2013-07-01

    We demonstrate the feasibility of the vessel-selective, non-contrast, time-resolved magnetic resonance angiography (MRA) technique, "contrast inherent inflow enhanced multi-phase angiography combining vessel-selective arterial spin labeling technique (CINEMA-SELECT)". This sequence consists of two major techniques: pulsed star labeling of arterial regions (PULSAR) and Look-Locker sampling. We hypothesize that this technique allows selective labeling of single intracranial arteries, consisting of high-resolution four-dimensional data with a wide coverage of the brain. In this study, a new vessel-selective, time-resolved angiographic technique is demonstrated that can produce individual angiograms non-invasively by labeling the principal arterial vessels proximal to the circle of Willis. Clear vessel delineation is achieved, and the separation of the three vessels is evident in healthy volunteers. This technique could play an important role in the assessment of the structure and hemodynamics of intracranial arteries without the use of contrast agents. PMID:23475783

  6. Mapping Long-Term Functional Changes in Cerebral Blood Flow by Arterial Spin Labeling

    PubMed Central

    Ssali, Tracy; Anazodo, Udunna C.; Bureau, Yves; MacIntosh, Bradley J.; Günther, Matthias; St. Lawrence, Keith

    2016-01-01

    Although arterial spin labeling (ASL) is appealing for mapping long-term changes in functional activity, inter-sessional variations in basal blood flow, arterial transit times (ATTs), and alignment errors, can result in significant false activation when comparing images from separate sessions. By taking steps to reduce these sources of noise, this study assessed the ability of ASL to detect functional CBF changes between sessions. ASL data were collected in three sessions to image ATT, resting CBF and CBF changes associated with motor activation (7 participants). Activation maps were generated using rest and task images acquired in the same session and from sessions separated by up to a month. Good agreement was found when comparing between-session activation maps to within-session activation maps with only a 16% decrease in precision (within-session: 90 ± 7%) and a 13% decrease in the Dice similarity (within-session: 0.75 ± 0.07) coefficient after a month. In addition, voxel-wise reproducibility (within-session: 4.7 ± 4.5%) and reliability (within-session: 0.89 ± 0.20) of resting grey-matter CBF decreased by less than 18% for the between-session analysis relative to within-session values. ATT variability between sessions (5.0 ± 2.7%) was roughly half the between-subject variability, indicating that its effects on longitudinal CBF were minimal. These results demonstrate that conducting voxel-wise analysis on CBF images acquired on different days is feasible with only modest loss in precision, highlighting the potential of ASL for longitudinal studies. PMID:27706218

  7. Discrete Li-occupation versus pseudo-continuous Na-occupation and their relationship with structural change behaviors in Fe₂(MoO₄)₃

    SciTech Connect

    Yue, Ji-Li; Zhou, Yong-Ning; Shi, Si-Qi; Shadike, Zulipiya; Huang, Xuan-Qi; Luo, Jun; Yang, Zhen-Zhong; Li, Hong; Gu, Lin; Yang, Xiao-Qing; Fu, Zheng-Wen

    2015-03-06

    The key factors governing the single-phase or multi-phase structural change behaviors during the intercalation/deintercalation of guest ions have not been well studied and understood yet. Through systematic studies of orthorhombic Fe₂(MoO₄)₃ electrode, two distinct guest ion occupation paths, namely discrete one for Li and pseudo-continuous one for Na, as well as their relationship with single-phase and two-phase modes for Na⁺ and Li⁺, respectively during the intercalation/deintercalation process have been demonstrated. For the first time, the direct atomic-scale observation of biphasic domains (discrete occupation) in partially lithiated Fe₂(MoO₄)₃ and the one by one Na occupation (pseudo-continuous occupation) at 8d sites in partially sodiated Fe₂(MoO₄)₃ are obtained during the discharge processes of Li/Fe₂(MoO₄)₃ and Na/Fe₂(MoO₄)₃ cells respectively. Our combined experimental and theoretical studies bring the new insights for the research and development of intercalation compounds as electrode materials for secondary batteries.

  8. Discrete Li-occupation versus pseudo-continuous Na-occupation and their relationship with structural change behaviors in Fe₂(MoO₄)₃

    DOE PAGES

    Yue, Ji-Li; Zhou, Yong-Ning; Shi, Si-Qi; Shadike, Zulipiya; Huang, Xuan-Qi; Luo, Jun; Yang, Zhen-Zhong; Li, Hong; Gu, Lin; Yang, Xiao-Qing; et al

    2015-03-06

    The key factors governing the single-phase or multi-phase structural change behaviors during the intercalation/deintercalation of guest ions have not been well studied and understood yet. Through systematic studies of orthorhombic Fe₂(MoO₄)₃ electrode, two distinct guest ion occupation paths, namely discrete one for Li and pseudo-continuous one for Na, as well as their relationship with single-phase and two-phase modes for Na⁺ and Li⁺, respectively during the intercalation/deintercalation process have been demonstrated. For the first time, the direct atomic-scale observation of biphasic domains (discrete occupation) in partially lithiated Fe₂(MoO₄)₃ and the one by one Na occupation (pseudo-continuous occupation) at 8d sites inmore » partially sodiated Fe₂(MoO₄)₃ are obtained during the discharge processes of Li/Fe₂(MoO₄)₃ and Na/Fe₂(MoO₄)₃ cells respectively. Our combined experimental and theoretical studies bring the new insights for the research and development of intercalation compounds as electrode materials for secondary batteries.« less

  9. Discrete Li-occupation versus pseudo-continuous Na-occupation and their relationship with structural change behaviors in Fe2(MoO4)3

    PubMed Central

    Yue, Ji-Li; Zhou, Yong-Ning; Shi, Si-Qi; Shadike, Zulipiya; Huang, Xuan-Qi; Luo, Jun; Yang, Zhen-Zhong; Li, Hong; Gu, Lin; Yang, Xiao-Qing; Fu, Zheng-Wen

    2015-01-01

    The key factors governing the single-phase or multi-phase structural change behaviors during the intercalation/deintercalation of guest ions have not been well studied and understood yet. Through systematic studies of orthorhombic Fe2(MoO4)3 electrode, two distinct guest ion occupation paths, namely discrete one for Li and pseudo-continuous one for Na, as well as their relationship with single-phase and two-phase modes for Na+ and Li+, respectively during the intercalation/deintercalation process have been demonstrated. For the first time, the direct atomic-scale observation of biphasic domains (discrete occupation) in partially lithiated Fe2(MoO4)3 and the one by one Na occupation (pseudo-continuous occupation) at 8d sites in partially sodiated Fe2(MoO4)3 are obtained during the discharge processes of Li/Fe2(MoO4)3 and Na/Fe2(MoO4)3 cells respectively. Our combined experimental and theoretical studies bring the new insights for the research and development of intercalation compounds as electrode materials for secondary batteries. PMID:25744589

  10. Cardiac arterial spin labeling using segmented ECG-gated Look-Locker FAIR: variability and repeatability in preclinical studies.

    PubMed

    Campbell-Washburn, Adrienne E; Price, Anthony N; Wells, Jack A; Thomas, David L; Ordidge, Roger J; Lythgoe, Mark F

    2013-01-01

    MRI is important for the assessment of cardiac structure and function in preclinical studies of cardiac disease. Arterial spin labeling techniques can be used to measure perfusion noninvasively. In this study, an electrocardiogram-gated Look-Locker sequence with segmented k-space acquisition has been implemented to acquire single slice arterial spin labeling data sets in 15 min in the mouse heart. A data logger was introduced to improve data quality by: (1) allowing automated rejection of respiration-corrupted images, (2) providing additional prospective gating to improve consistency of acquisition timing, and (3) allowing the recombination of uncorrupted k-space lines from consecutive data sets to reduce respiration corruption. Finally, variability and repeatability of perfusion estimation within-session, between-session, between-animal, and between image rejection criteria were assessed in mice. The criterion used to reject images from the T(1) fit was shown to affect the perfusion estimation. These data showed that the between-animal coefficient of variability (24%) was greater than the between-session variability (17%) and within-session variability (11%). Furthermore, the magnitude of change in perfusion required to detect differences was 30% (within-session) and 55% (between-session) according to Bland-Altman repeatability analysis. These technique developments and repeatability statistics will provide a platform for future preclinical studies applying cardiac arterial spin labeling.

  11. Combined Diffusion Tensor Imaging and Arterial Spin Labeling as Markers of Early Parkinson's disease.

    PubMed

    Wei, Xiaobo; Yan, Ronghua; Chen, Zhaoyu; Weng, Ruihui; Liu, Xu; Gao, Huimin; Xu, Xiaofeng; Kang, Zhuang; Liu, Zhexing; Guo, Yan; Liu, Zhenhua; Larsen, Jan Petter; Wang, Jin; Tang, Beisha; Hallett, Mark; Wang, Qing

    2016-09-20

    This study aimed to identify a PD-specific MRI pattern using combined diffusion tensor imaging (DTI) and arterial spin labeling (ASL) to discriminate patients with early PD from healthy subjects and evaluate disease status. Twenty-one early and 22 mid-late PD patients, and 22 healthy, age/gender-matched controls underwent 3-T MRI with apparent diffusion coefficient (ADC), fractional anisotropy (FA), fiber number (FN) and cerebral blood flow (CBF) measurements. We found that compared with healthy subjects, there was a profound reduction in FN passing through the SN in PD. FA in the SN and CBF in the caudate nucleus were inversely correlated with motor dysfunction. A negative correlation was observed between FA in the hippocampus (Hip) and the NMSS-Mood score, whereas CBF in the Hip and the prefrontal cortex(PFC) correlated with declined cognition. Stratified five-fold cross-validation identified FA in the SN(FA-SNAv), CBF in the PFC(CBF-PFCAv) and FA in the parietal white matter(FA-PWMAv), and the combination of these measurements offered relatively high accuracy (AUC 0.975, 90% sensitivity and 100% specificity) in distinguishing those with early PD from healthy subjects. We demonstrate that the decreased FNs through SN in combination with changes in FA-SNAv, CBF-PFCAv and FA-PWMAv values might serve as potential markers of early-stage PD.

  12. Human brain: reliability and reproducibility of pulsed arterial spin-labeling perfusion MR imaging.

    PubMed

    Jahng, Geon-Ho; Song, Enmin; Zhu, Xiao-Ping; Matson, Gerald B; Weiner, Michael W; Schuff, Norbert

    2005-03-01

    The Committee of Human Research of the University of California San Francisco approved this study, and all volunteers provided written informed consent. The goal of this study was to prospectively determine the global and regional reliability and reproducibility of noninvasive brain perfusion measurements obtained with different pulsed arterial spin-labeling (ASL) magnetic resonance (MR) imaging methods and to determine the extent to which within-subject variability and random noise limit reliability and reproducibility. Thirteen healthy volunteers were examined twice within 2 hours. The pulsed ASL methods compared in this study differ mainly with regard to magnetization transfer and eddy current effects. There were two main results: (a) Pulsed ASL MR imaging consistently had high measurement reliability (intraclass correlation coefficients greater than 0.75) and reproducibility (coefficients of variation less than 8.5%), and (b) random noise rather than within-subject variability limited reliability and reproducibility. It was concluded that low signal-to-noise ratios substantially limit the reliability and reproducibility of perfusion measurements.

  13. Arterial Spin Labeling Perfusion Study in the Patients with Subacute Mild Traumatic Brain Injury

    PubMed Central

    Lin, Che-Ming; Tseng, Ying-Chi; Hsu, Hui-Ling; Chen, Chi-Jen; Chen, David Yen-Ting; Yan, Feng-Xian; Chiu, Wen-Ta

    2016-01-01

    Background This study uses a MRI technique, three-dimension pulse continuous arterial spin labeling (3D-PCASL), to measure the patient’s cerebral blood flow (CBF) at the subacute stage of mild traumatic brain injury (MTBI) in order to analyze the relationship between cerebral blood flow and neurocognitive deficits. Objective To provide the relationship between cortical CBF and neuropsychological dysfunction for the subacute MTBI patients. Methods After MTBI, perfusion MR imaging technique (3D-PCASL) measures the CBF of MTBI patients (n = 23) within 1 month and that of normal controls (n = 22) to determine the quantity and location of perfusion defect. The correlation between CBF abnormalities and cognitive deficits was elucidated by combining the results of the neuropsychological tests of the patients. Result We observed a substantial reduction in CBF in the bilateral frontal and left occipital cortex as compared with the normal persons. In addition, there were correlation between post concussive symptoms (including dizziness and simulator sickness) and CBF in the hypoperfused areas. The more severe symptom was correlated with higher CBF in bilateral frontal and left occipital lobes. Conclusion First, this study determined that despite no significant abnormality detected on conventional CT and MRI studies, hypoperfusion was observed in MTBI group using 3D-PCASL technique in subacute stage, which suggested that this approach may increase sensitivity to MTBI. Second, the correlation between CBF and the severity of post concussive symptoms suggested that changes in cerebral hemodynamics may play a role in pathophysiology underlies the symptoms. PMID:26871696

  14. Combined Diffusion Tensor Imaging and Arterial Spin Labeling as Markers of Early Parkinson’s disease

    PubMed Central

    Wei, Xiaobo; Yan, Ronghua; Chen, Zhaoyu; Weng, Ruihui; Liu, Xu; Gao, Huimin; Xu, Xiaofeng; Kang, Zhuang; Liu, Zhexing; Guo, Yan; Liu, Zhenhua; Larsen, Jan Petter; Wang, Jin; Tang, Beisha; Hallett, Mark; Wang, Qing

    2016-01-01

    This study aimed to identify a PD-specific MRI pattern using combined diffusion tensor imaging (DTI) and arterial spin labeling (ASL) to discriminate patients with early PD from healthy subjects and evaluate disease status. Twenty-one early and 22 mid-late PD patients, and 22 healthy, age/gender-matched controls underwent 3-T MRI with apparent diffusion coefficient (ADC), fractional anisotropy (FA), fiber number (FN) and cerebral blood flow (CBF) measurements. We found that compared with healthy subjects, there was a profound reduction in FN passing through the SN in PD. FA in the SN and CBF in the caudate nucleus were inversely correlated with motor dysfunction. A negative correlation was observed between FA in the hippocampus (Hip) and the NMSS-Mood score, whereas CBF in the Hip and the prefrontal cortex(PFC) correlated with declined cognition. Stratified five-fold cross-validation identified FA in the SN(FA-SNAv), CBF in the PFC(CBF-PFCAv) and FA in the parietal white matter(FA-PWMAv), and the combination of these measurements offered relatively high accuracy (AUC 0.975, 90% sensitivity and 100% specificity) in distinguishing those with early PD from healthy subjects. We demonstrate that the decreased FNs through SN in combination with changes in FA-SNAv, CBF-PFCAv and FA-PWMAv values might serve as potential markers of early-stage PD. PMID:27646647

  15. Application of Arterial Spin Labelling in the Assessment of Ocular Tissues

    PubMed Central

    Pontré, B.

    2016-01-01

    Arterial spin labelling (ASL) is a noninvasive magnetic resonance imaging (MRI) modality, capable of measuring blood perfusion without the use of a contrast agent. While ASL implementation for imaging the brain and monitoring cerebral blood flow has been reviewed in depth, the technique is yet to be widely used for ocular tissue imaging. The human retina is a very thin but highly stratified structure and it is also situated close to the surface of the body which is not ideal for MR imaging. Hence, the application of MR imaging and ASL in particular has been very challenging for ocular tissues and retina. That is despite the fact that almost all of retinal pathologies are accompanied by blood perfusion irregularities. In this review article, we have focused on the technical aspects of the ASL and their implications for its optimum adaptation for retinal blood perfusion monitoring. Retinal blood perfusion has been assessed through qualitative or invasive quantitative methods but the prospect of imaging flow using ASL would increase monitoring and assessment of retinal pathologies. The review provides details of ASL application in human ocular blood flow assessment. PMID:27066501

  16. Combined Diffusion Tensor Imaging and Arterial Spin Labeling as Markers of Early Parkinson's disease.

    PubMed

    Wei, Xiaobo; Yan, Ronghua; Chen, Zhaoyu; Weng, Ruihui; Liu, Xu; Gao, Huimin; Xu, Xiaofeng; Kang, Zhuang; Liu, Zhexing; Guo, Yan; Liu, Zhenhua; Larsen, Jan Petter; Wang, Jin; Tang, Beisha; Hallett, Mark; Wang, Qing

    2016-01-01

    This study aimed to identify a PD-specific MRI pattern using combined diffusion tensor imaging (DTI) and arterial spin labeling (ASL) to discriminate patients with early PD from healthy subjects and evaluate disease status. Twenty-one early and 22 mid-late PD patients, and 22 healthy, age/gender-matched controls underwent 3-T MRI with apparent diffusion coefficient (ADC), fractional anisotropy (FA), fiber number (FN) and cerebral blood flow (CBF) measurements. We found that compared with healthy subjects, there was a profound reduction in FN passing through the SN in PD. FA in the SN and CBF in the caudate nucleus were inversely correlated with motor dysfunction. A negative correlation was observed between FA in the hippocampus (Hip) and the NMSS-Mood score, whereas CBF in the Hip and the prefrontal cortex(PFC) correlated with declined cognition. Stratified five-fold cross-validation identified FA in the SN(FA-SNAv), CBF in the PFC(CBF-PFCAv) and FA in the parietal white matter(FA-PWMAv), and the combination of these measurements offered relatively high accuracy (AUC 0.975, 90% sensitivity and 100% specificity) in distinguishing those with early PD from healthy subjects. We demonstrate that the decreased FNs through SN in combination with changes in FA-SNAv, CBF-PFCAv and FA-PWMAv values might serve as potential markers of early-stage PD. PMID:27646647

  17. Medial Occipital Lobe Hyperperfusion Identified by Arterial Spin-Labeling: A Poor Prognostic Sign in Patients with Hypoxic-Ischemic Encephalopathy.

    PubMed

    de Havenon, A; Sultan-Qurraie, A; Tirschwell, D; Cohen, W; Majersik, J; Andre, J B

    2015-12-01

    Hypoxic-ischemic encephalopathy carries an uncertain prognosis. We sought to retrospectively assess the prognostic value of arterial spin-labeling MR imaging in 22 adult patients diagnosed with hypoxic-ischemic encephalopathy. Quantitative CBF maps were generated from the M0 map, and arterial spin-labeling data on a per-voxel basis were regionally interrogated via visual inspection and ROI placement. Hyperperfusion was defined as regional increases in CBF of >20% (relative to global CBF) and/or >100 mL/100 g/min. Eleven of 22 patients had prominent bilateral medial occipital lobe hyperperfusion, all of whom died before hospital discharge. One patient who had nondistinct arterial spin-labeling hyperperfusion and restricted diffusion survived. Medial occipital lobe hyperperfusion is a distinctive pattern that merits prospective investigation in a cohort of patients with moderate hypoxic-ischemic encephalopathy to determine its predictive ability in patients with a higher likelihood of survival.

  18. Pulsed arterial spin labeling effectively and dynamically observes changes in cerebral blood flow after mild traumatic brain injury.

    PubMed

    Peng, Shu-Ping; Li, Yi-Ning; Liu, Jun; Wang, Zhi-Yuan; Zhang, Zi-Shu; Zhou, Shun-Ke; Tao, Fang-Xu; Zhang, Zhi-Xue

    2016-02-01

    Cerebral blood flow is strongly associated with brain function, and is the main symptom and diagnostic basis for a variety of encephalopathies. However, changes in cerebral blood flow after mild traumatic brain injury remain poorly understood. This study sought to observe changes in cerebral blood flow in different regions after mild traumatic brain injury using pulsed arterial spin labeling. Our results demonstrate maximal cerebral blood flow in gray matter and minimal in the white matter of patients with mild traumatic brain injury. At the acute and subacute stages, cerebral blood flow was reduced in the occipital lobe, parietal lobe, central region, subcutaneous region, and frontal lobe. Cerebral blood flow was restored at the chronic stage. At the acute, subacute, and chronic stages, changes in cerebral blood flow were not apparent in the insula. Cerebral blood flow in the temporal lobe and limbic lobe diminished at the acute and subacute stages, but was restored at the chronic stage. These findings suggest that pulsed arterial spin labeling can precisely measure cerebral blood flow in various brain regions, and may play a reference role in evaluating a patient's condition and judging prognosis after traumatic brain injury. PMID:27073378

  19. Pulsed arterial spin labeling effectively and dynamically observes changes in cerebral blood flow after mild traumatic brain injury

    PubMed Central

    Peng, Shu-ping; Li, Yi-ning; Liu, Jun; Wang, Zhi-yuan; Zhang, Zi-shu; Zhou, Shun-ke; Tao, Fang-xu; Zhang, Zhi-xue

    2016-01-01

    Cerebral blood flow is strongly associated with brain function, and is the main symptom and diagnostic basis for a variety of encephalopathies. However, changes in cerebral blood flow after mild traumatic brain injury remain poorly understood. This study sought to observe changes in cerebral blood flow in different regions after mild traumatic brain injury using pulsed arterial spin labeling. Our results demonstrate maximal cerebral blood flow in gray matter and minimal in the white matter of patients with mild traumatic brain injury. At the acute and subacute stages, cerebral blood flow was reduced in the occipital lobe, parietal lobe, central region, subcutaneous region, and frontal lobe. Cerebral blood flow was restored at the chronic stage. At the acute, subacute, and chronic stages, changes in cerebral blood flow were not apparent in the insula. Cerebral blood flow in the temporal lobe and limbic lobe diminished at the acute and subacute stages, but was restored at the chronic stage. These findings suggest that pulsed arterial spin labeling can precisely measure cerebral blood flow in various brain regions, and may play a reference role in evaluating a patient's condition and judging prognosis after traumatic brain injury. PMID:27073378

  20. Pseudo continuous wave instrument. [ultrasonics

    NASA Technical Reports Server (NTRS)

    Heyman, J. S. (Inventor)

    1978-01-01

    Acoustic properties and their changes in a sample of liquid, gas, plasma or solid are measured by applying a variable frequency source to the sample by means of a transducer to produce sound waves within the sample. The application of the variable frequency source to the sample is periodically interrupted for a short duration. Means are connected to the transducer for receiving the resulting acoustic signals during the interruptions for producing a control signal indicative of a difference in the frequency of the output of the variable frequency source and the frequency of a mechanical resonant peak in the sample. The control signal is applied to the variable frequency source to maintain its output frequency at the frequency of the mechanical resonant peak. The change in frequency of the variable frequency source indicates the shift in frequency of the mechanical resonant peak and the amplitude of the acoustic signals indicates the attenuation of the acoustic signals in the sample.

  1. SU-D-18C-05: Variable Bolus Arterial Spin Labeling MRI for Accurate Cerebral Blood Flow and Arterial Transit Time Mapping

    SciTech Connect

    Johnston, M; Jung, Y

    2014-06-01

    Purpose: Arterial spin labeling (ASL) is an MRI perfusion imaging method from which quantitative cerebral blood flow (CBF) maps can be calculated. Acquisition with variable post-labeling delays (PLD) and variable TRs allows for arterial transit time (ATT) mapping and leads to more accurate CBF quantification with a scan time saving of 48%. In addition, T1 and M0 maps can be obtained without a separate scan. In order to accurately estimate ATT and T1 of brain tissue from the ASL data, variable labeling durations were invented, entitled variable-bolus ASL. Methods: All images were collected on a healthy subject with a 3T Siemens Skyra scanner. Variable-bolus Psuedo-continuous ASL (PCASL) images were collected with 7 TI times ranging 100-4300ms in increments of 700ms with TR ranging 1000-5200ms. All boluses were 1600ms when the TI allowed, otherwise the bolus duration was 100ms shorter than the TI. All TI times were interleaved to reduce sensitivity to motion. Voxel-wise T1 and M0 maps were estimated using a linear least squares fitting routine from the average singal from each TI time. Then pairwise subtraction of each label/control pair and averaging for each TI time was performed. CBF and ATT maps were created using the standard model by Buxton et al. with a nonlinear fitting routine using the T1 tissue map. Results: CBF maps insensitive to ATT were produced along with ATT maps. Both maps show patterns and averages consistent with literature. The T1 map also shows typical T1 contrast. Conclusion: It has been demonstrated that variablebolus ASL produces CBF maps free from the errors due to ATT and tissue T1 variations and provides M0, T1, and ATT maps which have potential utility. This is accomplished with a single scan in a feasible scan time (under 6 minutes) with low sensivity to motion.

  2. Evaluation of Intracranial Vasculatures in Healthy Subjects with Arterial-Spin-Labeling-Based 4D-MR Angiography at 3T.

    PubMed

    Iryo, Yasuhiko; Hirai, Toshinori; Nakamura, Masanobu; Tateishi, Machiko; Hayashida, Eri; Azuma, Minako; Nishimura, Shinichiro; Kitajima, Mika; Yamashita, Yasuyuki

    2016-07-11

    Contrast inherent inflow-enhanced multi-phase angiography combining multiple-phase flow-alternating inversion-recovery (CINEMA-FAIR) is an arterial-spin-labeling-based four-dimensional magnetic resonance angiography (4D-MRA) technique. Two neuroradiologists independently evaluated the depiction of the intracranial vasculatures in healthy subjects with 3T 4D-MRA using CINEMA-FAIR. Our results indicated that this technique can provide good visualization of the cerebral arteries with a high spatial and temporal resolution. It appears to have sufficient resolution for identifying flow difference in the anterior and posterior circulation in healthy subjects. PMID:26701696

  3. Determination of skeletal muscle perfusion using arterial spin labeling NMRI: validation by comparison with venous occlusion plethysmography.

    PubMed

    Raynaud, J S; Duteil, S; Vaughan, J T; Hennel, F; Wary, C; Leroy-Willig, A; Carlier, P G

    2001-08-01

    T(1)-based determination of perfusion was performed with the high temporal and spatial resolution that monitoring of exercise physiology requires. As no data were available on the validation of this approach in human muscles, T(1)-based NMRI of perfusion was compared to standard strain-gauge venous occlusion plethysmography performed simultaneously within a 4 T magnet. Two different situations were investigated in 21 healthy young volunteers: 1) a 5-min ischemia of the leg, or 2) a 2-3 min ischemic exercise consisting of a plantar flexion on an amagnetic ergometer. Leg perfusion was monitored over 5-15 min of the recovery phase, after the air-cuff arterial occlusion had been released. The interesting features of the sequence were the use of a saturation-recovery module for the introduction of a T(1) modulation and of single-shot spin echo for imaging. Spatial resolution was 1.7 x 2.0 mm and temporal resolution was 2 s. For data analysis, ROIs were traced on different muscles and perfusion was calculated from the differences in muscle signal intensity in successive images. To allow comparison with the global measurement of perfusion by plethysmography, the T(1)-based NMR measurements in exercising muscles were rescaled to the leg cross-section. The perfusion measurements obtained by plethysmography and NMRI were in close agreement with a correlation coefficient between 0.87 and 0.92. This indicates that pulsed arterial techniques provide determination of muscle perfusion not only with superior spatial and temporal resolution but also with exactitude.

  4. The QUASAR reproducibility study, Part II: Results from a multi-center Arterial Spin Labeling test-retest study.

    PubMed

    Petersen, Esben Thade; Mouridsen, Kim; Golay, Xavier

    2010-01-01

    Arterial Spin Labeling (ASL) is a method to measure perfusion using magnetically labeled blood water as an endogenous tracer. Being fully non-invasive, this technique is attractive for longitudinal studies of cerebral blood flow in healthy and diseased individuals, or as a surrogate marker of metabolism. So far, ASL has been restricted mostly to specialist centers due to a generally low SNR of the method and potential issues with user-dependent analysis needed to obtain quantitative measurement of cerebral blood flow (CBF). Here, we evaluated a particular implementation of ASL (called Quantitative STAR labeling of Arterial Regions or QUASAR), a method providing user independent quantification of CBF in a large test-retest study across sites from around the world, dubbed "The QUASAR reproducibility study". Altogether, 28 sites located in Asia, Europe and North America participated and a total of 284 healthy volunteers were scanned. Minimal operator dependence was assured by using an automatic planning tool and its accuracy and potential usefulness in multi-center trials was evaluated as well. Accurate repositioning between sessions was achieved with the automatic planning tool showing mean displacements of 1.87+/-0.95 mm and rotations of 1.56+/-0.66 degrees . Mean gray matter CBF was 47.4+/-7.5 [ml/100 g/min] with a between-subject standard variation SD(b)=5.5 [ml/100 g/min] and a within-subject standard deviation SD(w)=4.7 [ml/100 g/min]. The corresponding repeatability was 13.0 [ml/100 g/min] and was found to be within the range of previous studies.

  5. Impact of neonate haematocrit variability on the longitudinal relaxation time of blood: Implications for arterial spin labelling MRI

    PubMed Central

    De Vis, J.B.; Hendrikse, J.; Groenendaal, F.; de Vries, L.S.; Kersbergen, K.J.; Benders, M.J.N.L.; Petersen, E.T.

    2014-01-01

    Background and purpose The longitudinal relaxation time of blood (T1b) is influenced by haematocrit (Hct) which is known to vary in neonates. The purpose of this study was threefold: to obtain T1b values in neonates, to investigate how the T1b influences quantitative arterial spin labelling (ASL), and to evaluate if known relationships between T1b and haematocrit (Hct) hold true when Hct is measured by means of a point-of-care device. Materials and methods One hundred and four neonates with 120 MR scan sessions (3 T) were included. The T1b was obtained from a T1 inversion recovery sequence. T1b-induced changes in ASL cerebral blood flow estimates were evaluated. The Hct was obtained by means of a point-of-care device. Linear regression analysis was used to investigate the relation between Hct and MRI-derived R1 of blood (the inverse of the T1b). Results Mean T1b was 1.85 s (sd 0.2 s). The mean T1b in preterm neonates was 1.77 s, 1.89 s in preterm neonates scanned at term-equivalent age (TEA) and 1.81 s in diseased neonates. The T1b in the TEA was significantly different from the T1b in the preterm (p < 0.05). The change in perfusion induced by the T1b was −11% (sd 9.1%, p < 0.001). The relation between arterial-drawn Hct and R1b was R1b = 0.80 × Hct + 0.22, which falls within the confidence interval of the previously established relationships, whereas capillary-drawn Hct did not correlate with R1b. Conclusion We demonstrated a wide variability of the T1b in neonates and the implications it could have in methods relying on the actual T1b as for instance ASL. It was concluded that arterial-drawn Hct values obtained from a point-of-care device can be used to infer the T1b whereas our data did not support the use of capillary-drawn Hct for T1b correction. PMID:24818078

  6. Acute effects of alcohol on brain perfusion monitored with arterial spin labeling magnetic resonance imaging in young adults.

    PubMed

    Marxen, Michael; Gan, Gabriela; Schwarz, Daniel; Mennigen, Eva; Pilhatsch, Maximilian; Zimmermann, Ulrich S; Guenther, Matthias; Smolka, Michael N

    2014-03-01

    While a number of studies have established that moderate doses of alcohol increase brain perfusion, the time course of such an increase as a function of breath alcohol concentration (BrAC) has not yet been investigated, and studies differ about regional effects. Using arterial spin labeling (ASL) magnetic resonance imaging, we investigated (1) the time course of the perfusion increase during a 15-minute linear increase of BrAC up to 0.6 g/kg followed by a steady exposure of 100 minutes, (2) the regional distribution, (3) a potential gender effect, and (4) the temporal stability of perfusion effects. In 48 young adults who participated in the Dresden longitudinal study on alcohol effects in young adults, we observed (1) a 7% increase of global perfusion as compared with placebo and that perfusion and BrAC are tightly coupled in time, (2) that the increase reaches significance in most regions of the brain, (3) that the effect is stronger in women than in men, and (4) that an acute tolerance effect is not observable on the time scale of 2 hours. Larger studies are needed to investigate the origin and the consequences of the effect, as well as the correlates of inter-subject variations.

  7. The effect of black tea and caffeine on regional cerebral blood flow measured with arterial spin labeling

    PubMed Central

    Vidyasagar, Rishma; Greyling, Arno; Draijer, Richard; Corfield, Douglas R; Parkes, Laura M

    2013-01-01

    Black tea consumption has been shown to improve peripheral vascular function. Its effect on brain vasculature is unknown, though tea contains small amounts of caffeine, a psychoactive substance known to influence cerebral blood flow (CBF). We investigated the effects on CBF due to the intake of tea components in 20 healthy men in a double-blinded, randomized, placebo-controlled study. On separate days, subjects received a single dose of 184 mg caffeine (equivalent to one strong espresso coffee), 2,820 mg black tea solids containing 184 mg caffeine (equivalent to 6 cups of tea), 2,820 mg decaffeinated black tea solids, or placebo. The CBF and cerebrovascular reactivity (CVR) to hypercapnia were measured with arterial spin labeled magnetic resonance imaging (MRI) before and 2 hours after administration. We found a significant global reduction with caffeine (20%) and tea (21%) in gray matter CBF, with no effect of decaffeinated tea, suggesting that only caffeine influences CBF acutely. Voxelwise analysis revealed the effect of caffeine to be regionally specific. None of the interventions had an effect on CVR. Additional research is required to conclude on the physiologic relevance of these findings and the chronic effects of caffeine and tea intake on CBF. PMID:23486295

  8. Comparison of Intravoxel Incoherent Motion Diffusion-Weighted MR Imaging and Arterial Spin Labeling MR Imaging in Gliomas

    PubMed Central

    Zhang, Zhiqiang; Zhou, Zhenyu; Zhang, Zhongping; Zhang, Yong; Zhang, Zongjun

    2015-01-01

    Gliomas grading is important for treatment plan; we aimed to investigate the application of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) in gliomas grading, by comparing with the three-dimensional pseudocontinuous arterial spin labeling (3D pCASL). 24 patients (13 high grade gliomas and 11 low grade gliomas) underwent IVIM DWI and 3D pCASL imaging before operation; maps of fast diffusion coefficient (D∗), slow diffusion coefficient (D), fractional perfusion-related volume (f), and apparent diffusion coefficient (ADC) as well as cerebral blood flow (CBF) were calculated and then coregistered to generate the corresponding parameter values. We found CBF and D∗ were higher in the high grade gliomas, whereas ADC, D, and f were lower (all P < 0.05). In differentiating the high from low grade gliomas, the maximum areas under the curves (AUC) of D∗, CBF, and ADC were 0.857, 0.85, and 0.902, respectively. CBF was negatively correlated with f in tumor (r = −0.619, P = 0.001). ADC was positively correlated with D in both tumor and white matter (r = 0.887, P = 0.000 and r = 0.824, P = 0.000, resp.). There was no correlation between CBF and D∗ in both tumor and white matter (P > 0.05). IVIM DWI showed more efficiency than 3D pCASL but less validity than conventional DWI in differentiating the high from low grade gliomas. PMID:25945328

  9. The effect of black tea and caffeine on regional cerebral blood flow measured with arterial spin labeling.

    PubMed

    Vidyasagar, Rishma; Greyling, Arno; Draijer, Richard; Corfield, Douglas R; Parkes, Laura M

    2013-06-01

    Black tea consumption has been shown to improve peripheral vascular function. Its effect on brain vasculature is unknown, though tea contains small amounts of caffeine, a psychoactive substance known to influence cerebral blood flow (CBF). We investigated the effects on CBF due to the intake of tea components in 20 healthy men in a double-blinded, randomized, placebo-controlled study. On separate days, subjects received a single dose of 184 mg caffeine (equivalent to one strong espresso coffee), 2,820 mg black tea solids containing 184 mg caffeine (equivalent to 6 cups of tea), 2,820 mg decaffeinated black tea solids, or placebo. The CBF and cerebrovascular reactivity (CVR) to hypercapnia were measured with arterial spin labeled magnetic resonance imaging (MRI) before and 2 hours after administration. We found a significant global reduction with caffeine (20%) and tea (21%) in gray matter CBF, with no effect of decaffeinated tea, suggesting that only caffeine influences CBF acutely. Voxelwise analysis revealed the effect of caffeine to be regionally specific. None of the interventions had an effect on CVR. Additional research is required to conclude on the physiologic relevance of these findings and the chronic effects of caffeine and tea intake on CBF. PMID:23486295

  10. Localization of the hand motor area by arterial spin labeling and blood oxygen level-dependent functional magnetic resonance imaging.

    PubMed

    Pimentel, Marco A F; Vilela, Pedro; Sousa, Inês; Figueiredo, Patrícia

    2013-01-01

    The new clinically available arterial spin labeling (ASL) perfusion imaging sequences present some advantages relatively to the commonly used blood oxygen level-dependent (BOLD) method for functional brain studies using magnetic resonance imaging (MRI). In particular, regional cerebral blood flow (CBF) changes are thought to be more directly related with neuronal activation. In this study, we aimed to investigate the accuracy of the functional localization of the hand motor area obtained by simultaneous CBF and BOLD contrasts provided by ASL functional MRI (fMRI) and compare it with a standard BOLD fMRI protocol. For this purpose, we measured the distance between the center of gravity of the activation clusters obtained with each contrast (CBF, BOLD(ASL), and Standard BOLD) and 11 positions defined on a well-established anatomical landmark of the hand motor area (the omega in the axial plane of the precentral gyrus). We found that CBF measurements were significantly closer to the anatomical landmark than the ones obtained using either simultaneous BOLD(ASL) or standard BOLD contrasts. Moreover, we also observed reduced intersubject variability of the functional localization, as well as percent signal change, for CBF relative to both BOLD contrast measurements. In conclusion, our results add further evidence in support to the notion that CBF provides a more accurate localization of motor activation than BOLD contrast, indicating that ASL may be an appropriate technique for clinical fMRI studies. PMID:22121040

  11. Voxel-Wise Functional Connectomics Using Arterial Spin Labeling Functional Magnetic Resonance Imaging: The Role of Denoising.

    PubMed

    Liang, Xiaoyun; Connelly, Alan; Calamante, Fernando

    2015-11-01

    The objective of this study was to investigate voxel-wise functional connectomics using arterial spin labeling (ASL) functional magnetic resonance imaging (fMRI). Since ASL signal has an intrinsically low signal-to-noise ratio (SNR), the role of denoising is evaluated; in particular, a novel denoising method, dual-tree complex wavelet transform (DT-CWT) combined with the nonlocal means (NLM) algorithm is implemented and evaluated. Simulations were conducted to evaluate the performance of the proposed method in denoising images and in detecting functional networks from noisy data (including the accuracy and sensitivity of detection). In addition, denoising was applied to in vivo ASL datasets, followed by network analysis using graph theoretical approaches. Efficiencies cost was used to evaluate the performance of denoising in detecting functional networks from in vivo ASL fMRI data. Simulations showed that denoising is effective in detecting voxel-wise functional networks from low SNR data and/or from data with small total number of time points. The capability of denoised voxel-wise functional connectivity analysis was also demonstrated with in vivo data. We concluded that denoising is important for voxel-wise functional connectivity using ASL fMRI and that the proposed DT-CWT-NLM method should be a useful ASL preprocessing step.

  12. The effect of black tea and caffeine on regional cerebral blood flow measured with arterial spin labeling.

    PubMed

    Vidyasagar, Rishma; Greyling, Arno; Draijer, Richard; Corfield, Douglas R; Parkes, Laura M

    2013-06-01

    Black tea consumption has been shown to improve peripheral vascular function. Its effect on brain vasculature is unknown, though tea contains small amounts of caffeine, a psychoactive substance known to influence cerebral blood flow (CBF). We investigated the effects on CBF due to the intake of tea components in 20 healthy men in a double-blinded, randomized, placebo-controlled study. On separate days, subjects received a single dose of 184 mg caffeine (equivalent to one strong espresso coffee), 2,820 mg black tea solids containing 184 mg caffeine (equivalent to 6 cups of tea), 2,820 mg decaffeinated black tea solids, or placebo. The CBF and cerebrovascular reactivity (CVR) to hypercapnia were measured with arterial spin labeled magnetic resonance imaging (MRI) before and 2 hours after administration. We found a significant global reduction with caffeine (20%) and tea (21%) in gray matter CBF, with no effect of decaffeinated tea, suggesting that only caffeine influences CBF acutely. Voxelwise analysis revealed the effect of caffeine to be regionally specific. None of the interventions had an effect on CVR. Additional research is required to conclude on the physiologic relevance of these findings and the chronic effects of caffeine and tea intake on CBF.

  13. Application of 3.0T magnetic resonance arterial spin labeling (ASL) technology in mild and moderate intracranial atherosclerotic stenosis

    PubMed Central

    LI, ZHONGWEI; LI, NAIKUN; QU, YANYAN; GAI, FENG; ZHANG, GUOWEI; ZHANG, GUANGHUI

    2016-01-01

    The application value of 3.0T magnetic resonance arterial spin labeling (ASL) technology in mild and moderate intracranial atherosclerotic stenosis was evaluated. A total of 58 cases of transient ischemic attack (TIA) and 60 cases of ischemic cerebral apoplexy cases were selected. The cases were analysed using a GE Healthcare Signa HDx 3.0T superconducting whole-body magnetic resonance scan within 24 h of attack. Eight-channel head phased array coils and conventional sequence were used to create T1-weighted images (T1WI), T2WI, diffusion-weighted imaging, magnetic resonance angiography (MRA) and ASL imaging, which were generated into ASL pseudo-color images (blue was hypoperfusion area) through post-processing in order to compare and analyze the correlation and differences between ASL and conventional imaging in terms of lesion location, size, blood perfusion situation and signal range of relative cerebral blood flow (rCBF). The results showed that, 13 TIA cases of abnormal signal in conventional magnetic resonance imaging (MRI) can also be found through ASL technology. Diameter stenosis beyond 30% in MRA can also be tested in ASL. A positive rate in ASL was significantly higher than that of conventional MRI (χ2=29.078, P<0.001) and hypoperfusion area was greatly increased (t=32.526, P<0.001). The rCBF value was positively correlated with the degree of diameter stenosis shown in MRA (r=0.524, P=0.012). Additionally, the positive rate of ASL was positively correlated with the attack times of TIA (r=0.352, P=0.027). A total of 39 cerebral apoplexy cases of abnormal signal in conventional MRI were also found through ASL technology. A positive rate in ASL was significantly higher than that of conventional MRI (χ2=7.685, P=0.006) and hypoperfusion area was greatly increased (t=9.425, P<0.001). The rCBF value was positively correlated with the degree of diameter stenosis (r=0.635, P=0.009). In conclusion, 3.0T ASL correlated with early diagnosis of TIA and mild and

  14. The Cerebral Blood Flow Biomedical Informatics Research Network (CBFBIRN) database and analysis pipeline for arterial spin labeling MRI data.

    PubMed

    Shin, David D; Ozyurt, I Burak; Liu, Thomas T

    2013-01-01

    Arterial spin labeling (ASL) is a magnetic resonance imaging technique that provides a non-invasive and quantitative measure of cerebral blood flow (CBF). After more than a decade of active research, ASL is now emerging as a robust and reliable CBF measurement technique with increased availability and ease of use. There is a growing number of research and clinical sites using ASL for neuroscience research and clinical care. In this paper, we present an online CBF Database and Analysis Pipeline, collectively called the Cerebral Blood Flow Biomedical Informatics Research Network (CBFBIRN) that allows researchers to upload and share ASL and clinical data. In addition to serving the role as a central data repository, the CBFBIRN provides a streamlined data processing infrastructure for CBF quantification and group analysis, which has the potential to accelerate the discovery of new scientific and clinical knowledge. All capabilities and features built into the CBFBIRN are accessed online using a web browser through a secure login. In this work, we begin with a general description of the CBFBIRN system data model and its architecture, then devote the remainder of the paper to the CBFBIRN capabilities. The latter part of our work is divided into two processing modules: (1) Data Upload and CBF Quantification Module; (2) Group Analysis Module that supports three types of analysis commonly used in neuroscience research. To date, the CBFBIRN hosts CBF maps and associated clinical data from more than 1,300 individual subjects. The data have been contributed by more than 20 different research studies, investigating the effect of various conditions on CBF including Alzheimer's, schizophrenia, bipolar disorder, depression, traumatic brain injury, HIV, caffeine usage, and methamphetamine abuse. Several example results, generated by the CBFBIRN processing modules, are presented. We conclude with the lessons learned during implementation and deployment of the CBFBIRN and our

  15. The Cerebral Blood Flow Biomedical Informatics Research Network (CBFBIRN) database and analysis pipeline for arterial spin labeling MRI data

    PubMed Central

    Shin, David D.; Ozyurt, I. Burak; Liu, Thomas T.

    2013-01-01

    Arterial spin labeling (ASL) is a magnetic resonance imaging technique that provides a non-invasive and quantitative measure of cerebral blood flow (CBF). After more than a decade of active research, ASL is now emerging as a robust and reliable CBF measurement technique with increased availability and ease of use. There is a growing number of research and clinical sites using ASL for neuroscience research and clinical care. In this paper, we present an online CBF Database and Analysis Pipeline, collectively called the Cerebral Blood Flow Biomedical Informatics Research Network (CBFBIRN) that allows researchers to upload and share ASL and clinical data. In addition to serving the role as a central data repository, the CBFBIRN provides a streamlined data processing infrastructure for CBF quantification and group analysis, which has the potential to accelerate the discovery of new scientific and clinical knowledge. All capabilities and features built into the CBFBIRN are accessed online using a web browser through a secure login. In this work, we begin with a general description of the CBFBIRN system data model and its architecture, then devote the remainder of the paper to the CBFBIRN capabilities. The latter part of our work is divided into two processing modules: (1) Data Upload and CBF Quantification Module; (2) Group Analysis Module that supports three types of analysis commonly used in neuroscience research. To date, the CBFBIRN hosts CBF maps and associated clinical data from more than 1,300 individual subjects. The data have been contributed by more than 20 different research studies, investigating the effect of various conditions on CBF including Alzheimer’s, schizophrenia, bipolar disorder, depression, traumatic brain injury, HIV, caffeine usage, and methamphetamine abuse. Several example results, generated by the CBFBIRN processing modules, are presented. We conclude with the lessons learned during implementation and deployment of the CBFBIRN and our

  16. Partial volume correction of brain perfusion estimates using the inherent signal data of time-resolved arterial spin labeling.

    PubMed

    Ahlgren, André; Wirestam, Ronnie; Petersen, Esben Thade; Ståhlberg, Freddy; Knutsson, Linda

    2014-09-01

    Quantitative perfusion MRI based on arterial spin labeling (ASL) is hampered by partial volume effects (PVEs), arising due to voxel signal cross-contamination between different compartments. To address this issue, several partial volume correction (PVC) methods have been presented. Most previous methods rely on segmentation of a high-resolution T1 -weighted morphological image volume that is coregistered to the low-resolution ASL data, making the result sensitive to errors in the segmentation and coregistration. In this work, we present a methodology for partial volume estimation and correction, using only low-resolution ASL data acquired with the QUASAR sequence. The methodology consists of a T1 -based segmentation method, with no spatial priors, and a modified PVC method based on linear regression. The presented approach thus avoids prior assumptions about the spatial distribution of brain compartments, while also avoiding coregistration between different image volumes. Simulations based on a digital phantom as well as in vivo measurements in 10 volunteers were used to assess the performance of the proposed segmentation approach. The simulation results indicated that QUASAR data can be used for robust partial volume estimation, and this was confirmed by the in vivo experiments. The proposed PVC method yielded probable perfusion maps, comparable to a reference method based on segmentation of a high-resolution morphological scan. Corrected gray matter (GM) perfusion was 47% higher than uncorrected values, suggesting a significant amount of PVEs in the data. Whereas the reference method failed to completely eliminate the dependence of perfusion estimates on the volume fraction, the novel approach produced GM perfusion values independent of GM volume fraction. The intra-subject coefficient of variation of corrected perfusion values was lowest for the proposed PVC method. As shown in this work, low-resolution partial volume estimation in connection with ASL perfusion

  17. Implication of cerebral circulation time in intracranial stenosis measured by digital subtraction angiography on cerebral blood flow estimation measured by arterial spin labeling

    PubMed Central

    Jann, Kay; Hauf, Martinus; Kellner-Weldon, Frauke; El-Koussy, Marwan; Kiefer, Claus; Federspiel, Andrea; Schroth, Gerhard

    2016-01-01

    PURPOSE Arterial spin labeling (ASL) magnetic resonance imaging to assess cerebral blood flow (CBF) is of increasing interest in basic research and in diagnostic applications, since ASL provides similar information to positron emission tomography about perfusion in vascular territories. However, in patients with steno-occlusive arterial disease (SOAD), CBF as measured by ASL might be underestimated due to delayed bolus arrival, and thus increased spin relaxation. We aimed to estimate the extent to which bolus arrival time (BAT) was delayed in patients with SOAD and whether this resulted in underestimation of CBF. METHODS BAT was measured using digital subtraction angiography (DSA) in ten patients with high-grade stenosis of the middle carotid artery (MCA). Regional CBF was assessed with pseudocontinuous ASL. RESULTS BATs were nonsignificantly prolonged in the stenotic hemisphere 4.1±2.0 s compared with the healthy hemisphere 3.3±0.9 s; however, there were substantial individual differences on the stenotic side. CBF in the anterior and posterior MCA territories were significantly reduced on the stenotic hemisphere. Severe stenosis was correlated with longer BAT and lower quantified CBF. CONCLUSION ASL-based perfusion measurement involves a race between the decay of the spins and the delivery of labeled blood to the region of interest. Special caution is needed when interpreting CBF values quantified in individuals with altered blood flow and delayed circulation times. However, from a clinician’s point of view, an accentuation of hypoperfusion (even if caused by underestimation of CBF due to prolonged BATs) might be desirable since it indexes potentially harmful physiologic deficits. PMID:27411297

  18. Detection of preclinically latent hyperperfusion due to stroke-like episodes by arterial spin-labeling perfusion MRI in MELAS patients.

    PubMed

    Ikawa, Masamichi; Yoneda, Makoto; Muramatsu, Tomoko; Matsunaga, Akiko; Tsujikawa, Tetsuya; Yamamoto, Tatsuya; Kosaka, Nobuyuki; Kinoshita, Kazuyuki; Yamamura, Osamu; Hamano, Tadanori; Nakamoto, Yasunari; Kimura, Hirohiko

    2013-11-01

    In stroke-like episodes (SEs) of patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), the detection of preclinically latent lesions is a challenge. We report regional cerebral hyperperfusion observed on arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) in the preclinical phase more than 3 months before the clinical onset of SEs in 3 MELAS patients. These hyperperfused areas were not detected by conventional MRI in the preclinical phase and developed into acute lesions at the clinical onset of SEs, suggesting that ASL imaging has the potential for predicting the emergence of SEs.

  19. Time-efficient determination of spin compartments by time-encoded pCASL T2-relaxation-under-spin-tagging and its application in hemodynamic characterization of the cerebral border zones.

    PubMed

    Schmid, Sophie; Teeuwisse, Wouter M; Lu, Hanzhang; van Osch, Matthias J P

    2015-12-01

    Information on water-transport across the blood-brain barrier can be determined from the T2 of the arterial spin labeling (ASL) signal. However, the current approach of using separate acquisitions of multiple inversion times is too time-consuming for clinical (research) applications. The aim of this study was to improve the time-efficiency of this method by combining it with time-encoded pseudo-continuous ASL (te-pCASL). Furthermore, the hemodynamic properties of the border zone regions in the brains of healthy, young volunteers were characterized as an example application. The use of te-pCASL instead of multi-TI pCASL significantly reduced the total scan duration, while providing a higher temporal resolution. A significantly lower cerebral blood flow (CBF) was found in the border zone regions compared with the central regions in both the posterior and the middle cerebral artery (MCA) flow territory. The arterial transit time (ATT) was almost two times longer in the border zone regions than in the central regions (p<0.05), with an average delay in ATT of 382ms in the posterior and 539ms in the MCA flow territory. When corrected for the ATT, the change in T2 over time was not significantly different for the border zones as compared to the central regions. In conclusion, te-pCASL-TRUST provided a time-efficient method to distinguish spin compartments based on their T2. The ATT in the border zone is significantly longer than in the central region. However, the exchange of the label from the arterial to the tissue compartment appears to be at a similar rate.

  20. Cerebral blood flow changes in hemodialysis and peritoneal dialysis patients: an arterial-spin labeling MR imaging.

    PubMed

    Jiang, Xiao Lu; Wen, Ji Qiu; Zhang, Long Jiang; Zheng, Gang; Li, Xue; Zhang, Zhe; Liu, Ya; Zheng, Li Juan; Wu, Long; Chen, Hui Juan; Kong, Xiang; Luo, Song; Lu, Guang Ming; Ji, Xue Man; Zhang, Zong Jun

    2016-08-01

    We used arterial-spin labeling (ASL) MR imaging, a non-invasive technique to evaluate cerebral blood flow (CBF) changes in patients with end-stage renal disease (ESRD) undergoing peritoneal dialysis (PD) and hemodialysis (HD), and nondialysis ESRD patients compared with healthy cohort. Ninety seven ESRD patients including 32 PD patients (20 male, 12 female; mean age 33 ± 8 years), 33 HD patients (22 male, 11 female; mean age 33 ± 8 years) and 32 nondialysis patients (20 male, 12 female; mean age 35 ± 7 years) and 31 age- and gender-matched healthy controls (20 male, 11 female; mean age 32 ± 8 years) were included in this study. All subjects underwent ASL MR imaging, neuropsychologic tests, and ESRD patients underwent laboratory testing. CBF values were compared among PD, HD, nondialysis patients and control groups. Correlation analysis and multiple regression analysis were performed to investigate the association between CBF values and hemoglobin, neuropsychologic test results, serum creatinine, urea levels, disease duration, and dialysis duration. Elevated CBFs of whole brain region, gray matter, and white matter were found in all ESRD patient groups compared with healthy controls (all P < 0.001). However, compared with non-dialysis ESRD patients, both PD and HD patients had widespread regional CBF decline mainly in bilateral frontal and anterior cingulate cortices. There were no differences for CBF between PD and HD patient groups. Negative correlations were observed between mean CBFs of whole brain region, gray matter, and white matter and the hemoglobin level in all ESRD patients. Multiple linear regression showed elevated CBF of multiple brain areas correlated with some neuropsychological tests in ESRD patients (all P < 0.001, AlphaSim corrected), but the association was not present or shrank after adjusting hemoglobin level. This study found that mean CBF was predominantly increased in patients with ESRD, which correlated with their

  1. Patterns of postictal cerebral perfusion in idiopathic generalized epilepsy: a multi-delay multi-parametric arterial spin labelling perfusion MRI study

    PubMed Central

    Chen, Guangxiang; Lei, Du; Ren, Jiechuan; Zuo, Panli; Suo, Xueling; Wang, Danny J. J.; Wang, Meiyun; Zhou, Dong; Gong, Qiyong

    2016-01-01

    The cerebral haemodynamic status of idiopathic generalized epilepsy (IGE) is a very complicated process. Little attention has been paid to cerebral blood flow (CBF) alterations in IGE detected by arterial spin labelling (ASL) perfusion magnetic resonance imaging (MRI). However, the selection of an optimal delay time is difficult for single-delay ASL. Multi-delay multi-parametric ASL perfusion MRI overcomes the limitations of single-delay ASL. We applied multi-delay multi-parametric ASL perfusion MRI to investigate the patterns of postictal cerebral perfusion in IGE patients with absence seizures. A total of 21 IGE patients with absence seizures and 24 healthy control subjects were enrolled. IGE patients exhibited prolonged arterial transit time (ATT) in the left superior temporal gyrus. The mean CBF of IGE patients was significantly increased in the left middle temporal gyrus, left parahippocampal gyrus and left fusiform gyrus. Prolonged ATT in the left superior temporal gyrus was negatively correlated with the age at onset in IGE patients. This study demonstrated that cortical dysfunction in the temporal lobe and fusiform gyrus may be related to epileptic activity in IGE patients with absence seizures. This information can play an important role in elucidating the pathophysiological mechanism of IGE from a cerebral haemodynamic perspective. PMID:27374369

  2. [Abnormal cerebral blood flow distributions during the post-ictal phase of febrile status epilepticus in three pediatric patients measured by arterial spin labeling perfusion MRI].

    PubMed

    Hirano, Keiko; Fukuda, Tokiko

    2016-05-01

    The ability to visualize brain perfusion is important for identifying epileptic foci. We present three pediatric cases showing asymmetrical cerebral blood flow (CBF) distributions during the post-ictal phase of febrile status epilepticus measured by arterial spin labeling (ASL) perfusion MRI. During the acute phase, regional CBF measurements in the areas considered including epileptic foci were higher than in the corresponding area of the contralateral hemisphere, though the exact quantitative value varied between cases. We could not identify the correct epileptogenic foci, because those ASL images were taken after the prolonged and extraordinary activation of neurons in the affected area. During the recovery phase, the differences reduced and the average regional CBF measurement was 54.6 ± 6.1 ml/100 g per minute, which was a little less than the number of previous ASL studies. ASL perfusion MRI imaging provides a method for evaluating regional CBF by using magnetically labeled arterial blood water as an endogenous tracer. With this technique, we can repeatedly evaluate both the brain structure and the level of perfusion at the same time. ASL is noninvasive and easily accessible, and therefore it could become a routine tool for assessment of perfusion in daily practice of pediatric neurology. PMID:27349086

  3. Quantitative assessment of cerebral hemodynamic parameters by QUASAR arterial spin labeling in Alzheimer's disease and cognitively normal Elderly adults at 3-tesla.

    PubMed

    Mak, Henry K F; Chan, Queenie; Zhang, Zhipeng; Petersen, Esben T; Qiu, Deqiang; Zhang, Linda; Yau, Kelvin K W; Chu, Leung-Wing; Golay, Xavier

    2012-01-01

    QUASAR arterial spin labeling (ASL) was used to investigate the role of vascular impairment in Alzheimer's disease (AD). We hypothesized that the hemodynamic parameters monitoring cerebrovascular integrity, i.e., cerebral blood flow (CBF), arterial blood volume (aBV), and arterial transit time (aTT), would be affected. 13 AD patients and 15 healthy control (HC) subjects underwent 3T MRI scanning. Two separate blood flow acquisitions were obtained with 1 slice overlap for whole brain coverage. CBF, aBV, and aTT maps were calculated using in-house software. Preprocessing and statistical analyses were performed on SPM5. Region-of-interest (ROI) studies of ten selected cerebral regions were also conducted. There were significant differences in mini mental status exam (MMSE) (AD: 16.3 ± 4.55, HC: 28.5 ± 2.00) and Alzheimer's disease assessment scale-cognitive subscale (ADAS-cog) scores (AD: 25.25 ± 9.64, HC: 5.51 ± 2.62) between the 2 groups (p < 0.001) but none in age (p = 0.068). CBF decreased significantly (p < 0.01) in AD compared to controls in the right middle cingulate, left cuneus, left inferior and middle frontal, right superior frontal, left inferior parietal, and right supramarginal gyri. ROI studies confirmed significant hemodynamic impairments in AD compared to HC (p < 0.05): CBF in middle and posterior cingulate, aBV in left superior temporal, right inferior parietal, and posterior cingulate, and aTT in left inferior frontal and middle cingulate gyri. CBF correlated positively while aTT correlated negatively to MMSE, and vice versa for ADAS-cog. Using QUASAR ASL, we found patterns of regional hemodynamic impairment typical of moderate AD, suggesting underlying vascular abnormality. As potential biomarkers, these hemodynamic parameters could differentiate patients from volunteers, and possibly indicate the conversion from healthy aging to mild cognitive impairment to AD.

  4. Regional and voxel-wise comparisons of blood flow measurements between dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) and arterial spin labeling (ASL) in brain tumors.

    PubMed

    White, Carissa M; Pope, Whitney B; Zaw, Taryar; Qiao, Joe; Naeini, Kourosh M; Lai, Albert; Nghiemphu, Phioanh L; Wang, J J; Cloughesy, Timothy F; Ellingson, Benjamin M

    2014-01-01

    The objective of the current study was to evaluate the regional and voxel-wise correlation between dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) measurement of cerebral blood flow (CBF) in patients with brain tumors. Thirty patients with histologically verified brain tumors were evaluated in the current study. DSC-MRI was performed by first using a preload dose of gadolinium contrast, then collecting a dynamic image acquisition during a bolus of contrast, followed by posthoc contrast agent leakage correction. Pseudocontinuous ASL was collected using 30 pairs of tag and control acquisition using a 3-dimensional gradient-echo spin-echo (GRASE) acquisition. All images were registered to a high-resolution anatomical atlas. Average CBF measurements within regions of contrast-enhancement and T2 hyperintensity were evaluated between the two modalities. Additionally, voxel-wise correlation between CBF measurements obtained with DSC and ASL were assessed. Results demonstrated a positive linear correlation between DSC and ASL measurements of CBF when regional average values were compared; however, a statistically significant voxel-wise correlation was only observed in around 30-40% of patients. These results suggest DSC and ASL may provide regionally similar, but spatially different measurements of CBF.

  5. Optimization of 4D vessel‐selective arterial spin labeling angiography using balanced steady‐state free precession and vessel‐encoding

    PubMed Central

    Schmitt, Peter; Bi, Xiaoming; Chappell, Michael A.; Tijssen, Rob H. N.; Sheerin, Fintan; Miller, Karla L.; Jezzard, Peter

    2016-01-01

    Vessel‐selective dynamic angiograms provide a wealth of useful information about the anatomical and functional status of arteries, including information about collateral flow and blood supply to lesions. Conventional x‐ray techniques are invasive and carry some risks to the patient, so non‐invasive alternatives are desirable. Previously, non‐contrast dynamic MRI angiograms based on arterial spin labeling (ASL) have been demonstrated using both spoiled gradient echo (SPGR) and balanced steady‐state free precession (bSSFP) readout modules, but no direct comparison has been made, and bSSFP optimization over a long readout period has not been fully explored. In this study bSSFP and SPGR are theoretically and experimentally compared for dynamic ASL angiography. Unlike SPGR, bSSFP was found to have a very low ASL signal attenuation rate, even when a relatively large flip angle and short repetition time were used, leading to a threefold improvement in the measured signal‐to‐noise ratio (SNR) efficiency compared with SPGR. For vessel‐selective applications, SNR efficiency can be further improved over single‐artery labeling methods by using a vessel‐encoded pseudo‐continuous ASL (VEPCASL) approach. The combination of a VEPCASL preparation with a time‐resolved bSSFP readout allowed the generation of four‐dimensional (4D; time‐resolved three‐dimensional, 3D) vessel‐selective cerebral angiograms in healthy volunteers with 59 ms temporal resolution. Good quality 4D angiograms were obtained in all subjects, providing comparable structural information to 3D time‐of‐flight images, as well as dynamic information and vessel selectivity, which was shown to be high. A rapid 1.5 min dynamic two‐dimensional version of the sequence yielded similar image features and would be suitable for a busy clinical protocol. Preliminary experiments with bSSFP that included the extracranial vessels showed signal loss in regions of poor magnetic field

  6. Dopaminergic Therapy Modulates Cortical Perfusion in Parkinson Disease With and Without Dementia According to Arterial Spin Labeled Perfusion Magnetic Resonance Imaging

    PubMed Central

    Lin, Wei-Che; Chen, Pei-Chin; Huang, Yung-Cheng; Tsai, Nai-Wen; Chen, Hsiu-Ling; Wang, Hung-Chen; Lin, Tsu-Kung; Chou, Kun-Hsien; Chen, Meng-Hsiang; Chen, Yi-Wen; Lu, Cheng-Hsien

    2016-01-01

    Abstract Arterial spin labeling (ASL) magnetic resonance imaging analyses allow for the quantification of altered cerebral blood flow, and provide a novel means of examining the impact of dopaminergic treatments. The authors examined the cerebral perfusion differences among 17 Parkinson disease (PD) patients, 17 PD with dementia (PDD) patients, and 17 healthy controls and used ASL-MRI to assess the effects of dopaminergic therapies on perfusion in the patients. The authors demonstrated progressive widespread cortical hypoperfusion in PD and PDD and robust effects for the dopaminergic therapies. Specifically, dopaminergic medications further decreased frontal lobe and cerebellum perfusion in the PD and PDD groups, respectively. These patterns of hypoperfusion could be related to cognitive dysfunctions and disease severity. Furthermore, desensitization to dopaminergic therapies in terms of cortical perfusion was found as the disease progressed, supporting the concept that long-term therapies are associated with the therapeutic window narrowing. The highly sensitive pharmaceutical response of ASL allows clinicians and researchers to easily and effectively quantify the absolute perfusion status, which might prove helpful for therapeutic planning. PMID:26844450

  7. Noncontrast-enhanced three-dimensional (3D) intracranial MR angiography using pseudocontinuous arterial spin labeling and accelerated 3D radial acquisition.

    PubMed

    Wu, Huimin; Block, Walter F; Turski, Patrick A; Mistretta, Charles A; Johnson, Kevin M

    2013-03-01

    Pseudocontinuous arterial spin labeling (PCASL) can be used to generate noncontrast magnetic resonance angiograms of the cerebrovascular structures. Previously described PCASL-based angiography techniques were limited to two-dimensional projection images or relatively low-resolution three-dimensional (3D) imaging due to long acquisition time. This work proposes a new PCASL-based 3D magnetic resonance angiography method that uses an accelerated 3D radial acquisition technique (VIPR, spoiled gradient echo) as the readout. Benefiting from the sparsity provided by PCASL and noise-like artifacts of VIPR, this new method is able to obtain submillimeter 3D isotropic resolution and whole head coverage with a 8-min scan. Intracranial angiography feasibility studies in healthy (N = 5) and diseased (N = 5) subjects show reduced saturation artifacts in PCASL-VIPR compared with a standard time-of-flight protocol. These initial results show great promise for PCASL-VIPR for static, dynamic, and vessel selective 3D intracranial angiography. PMID:22532423

  8. Quantitative spatial comparison of diffuse optical imaging with blood oxygen level-dependent and arterial spin labeling-based functional magnetic resonance imaging

    PubMed Central

    Huppert, Theodore J.; Hoge, Rick D.; Dale, Anders M.; Franceschini, Maria A.; Boas, David A.

    2009-01-01

    Akin to functional magnetic resonance imaging (fMRI), diffuse optical imaging (DOI) is a noninvasive method for measuring localized changes in hemoglobin levels within the brain. When combined with fMRI methods, multimodality approaches could offer an integrated perspective on the biophysics, anatomy, and physiology underlying each of the imaging modalities. Vital to the correct interpretation of such studies, control experiments to test the consistency of both modalities must be performed. Here, we compare DOI with blood oxygen level-dependent (BOLD) and arterial spin labeling fMRI-based methods in order to explore the spatial agreement of the response amplitudes recorded by these two methods. Rather than creating optical images by regularized, tomographic reconstructions, we project the fMRI image into optical measurement space using the optical forward problem. We report statistically better spatial correlation between the fMRI-BOLD response and the optically measured deoxyhemoglobin (R=0.71, p=1 × 10−7) than between the BOLD and oxyhemoglobin or total hemoglobin measures (R=0.38, p=0.04|0.37, p=0.05, respectively). Similarly, we find that the correlation between the ASL measured blood flow and optically measured total and oxyhemoglobin is stronger (R=0.73, p=5 × 10−6 and R=0.71, p=9 × 10−6, respectively) than the flow to deoxyhemoglobin spatial correlation (R=0.26, p=0.10). PMID:17212541

  9. Dopaminergic Therapy Modulates Cortical Perfusion in Parkinson Disease With and Without Dementia According to Arterial Spin Labeled Perfusion Magnetic Resonance Imaging.

    PubMed

    Lin, Wei-Che; Chen, Pei-Chin; Huang, Yung-Cheng; Tsai, Nai-Wen; Chen, Hsiu-Ling; Wang, Hung-Chen; Lin, Tsu-Kung; Chou, Kun-Hsien; Chen, Meng-Hsiang; Chen, Yi-Wen; Lu, Cheng-Hsien

    2016-02-01

    Arterial spin labeling (ASL) magnetic resonance imaging analyses allow for the quantification of altered cerebral blood flow, and provide a novel means of examining the impact of dopaminergic treatments. The authors examined the cerebral perfusion differences among 17 Parkinson disease (PD) patients, 17 PD with dementia (PDD) patients, and 17 healthy controls and used ASL-MRI to assess the effects of dopaminergic therapies on perfusion in the patients. The authors demonstrated progressive widespread cortical hypoperfusion in PD and PDD and robust effects for the dopaminergic therapies. Specifically, dopaminergic medications further decreased frontal lobe and cerebellum perfusion in the PD and PDD groups, respectively. These patterns of hypoperfusion could be related to cognitive dysfunctions and disease severity. Furthermore, desensitization to dopaminergic therapies in terms of cortical perfusion was found as the disease progressed, supporting the concept that long-term therapies are associated with the therapeutic window narrowing. The highly sensitive pharmaceutical response of ASL allows clinicians and researchers to easily and effectively quantify the absolute perfusion status, which might prove helpful for therapeutic planning.

  10. Effects of background suppression on the sensitivity of dual-echo arterial spin labeling MRI for BOLD and CBF signal changes.

    PubMed

    Ghariq, Eidrees; Chappell, Michael A; Schmid, Sophie; Teeuwisse, Wouter M; van Osch, Matthias J P

    2014-12-01

    Dual-echo arterial spin labeling (DE-ASL) enables the simultaneous acquisition of BOLD and CBF fMRI data and is often used for calibrated BOLD and cerebrovascular CO2 reactivity measurements. DE-ASL, like all ASL techniques, suffers from a low intrinsic CBF SNR, which can be improved by suppressing the background signal via the inclusion of additional inversion pulses. However, until now this approach has been considered to be undesirable for DE-ASL, because the BOLD signal is extracted from the background signal and attenuating the background signal could decrease the sensitivity of DE-ASL scans for BOLD changes. In this study, the effect of background suppression on the sensitivity of DE-ASL MRI for BOLD and CBF signal changes with a visual stimulation paradigm was studied. Results showed that with an average background suppression level of 70% the BOLD sensitivity of DE-ASL MRI decreases slightly (15%), while the CBF sensitivity of the scans increased by almost a factor-of-two (81%). These findings support the conclusion that the gains in CBF sensitivity of DE-ASL MRI due to background suppression outweigh the slight decrease in sensitivity of these scans for BOLD changes, and thus that background suppression is highly recommended for DE-ASL.

  11. Computer-aided classification of patients with dementia of Alzheimer's type based on cerebral blood flow determined with arterial spin labeling technique

    NASA Astrophysics Data System (ADS)

    Yamashita, Yasuo; Arimura, Hidetaka; Yoshiura, Takashi; Tokunaga, Chiaki; Magome, Taiki; Monji, Akira; Noguchi, Tomoyuki; Toyofuku, Fukai; Oki, Masafumi; Nakamura, Yasuhiko; Honda, Hiroshi

    2010-03-01

    Arterial spin labeling (ASL) is one of promising non-invasive magnetic resonance (MR) imaging techniques for diagnosis of Alzheimer's disease (AD) by measuring cerebral blood flow (CBF). The aim of this study was to develop a computer-aided classification system for AD patients based on CBFs measured by the ASL technique. The average CBFs in cortical regions were determined as functional image features based on the CBF map image, which was non-linearly transformed to a Talairach brain atlas by using a free-form deformation. An artificial neural network (ANN) was trained with the CBF functional features in 10 cortical regions, and was employed for distinguishing patients with AD from control subjects. For evaluation of the method, we applied the proposed method to 20 cases including ten AD patients and ten control subjects, who were scanned a 3.0-Tesla MR unit. As a result, the area under the receiver operating characteristic curve obtained by the proposed method was 0.893 based on a leave-one-out-by-case test in identification of AD cases among 20 cases. The proposed method would be feasible for classification of patients with AD.

  12. Arterial spin labeling-fast imaging with steady-state free precession (ASL-FISP): a rapid and quantitative perfusion technique for high-field MRI.

    PubMed

    Gao, Ying; Goodnough, Candida L; Erokwu, Bernadette O; Farr, George W; Darrah, Rebecca; Lu, Lan; Dell, Katherine M; Yu, Xin; Flask, Chris A

    2014-08-01

    Arterial spin labeling (ASL) is a valuable non-contrast perfusion MRI technique with numerous clinical applications. Many previous ASL MRI studies have utilized either echo-planar imaging (EPI) or true fast imaging with steady-state free precession (true FISP) readouts, which are prone to off-resonance artifacts on high-field MRI scanners. We have developed a rapid ASL-FISP MRI acquisition for high-field preclinical MRI scanners providing perfusion-weighted images with little or no artifacts in less than 2 s. In this initial implementation, a flow-sensitive alternating inversion recovery (FAIR) ASL preparation was combined with a rapid, centrically encoded FISP readout. Validation studies on healthy C57/BL6 mice provided consistent estimation of in vivo mouse brain perfusion at 7 and 9.4 T (249 ± 38 and 241 ± 17 mL/min/100 g, respectively). The utility of this method was further demonstrated in the detection of significant perfusion deficits in a C57/BL6 mouse model of ischemic stroke. Reasonable kidney perfusion estimates were also obtained for a healthy C57/BL6 mouse exhibiting differential perfusion in the renal cortex and medulla. Overall, the ASL-FISP technique provides a rapid and quantitative in vivo assessment of tissue perfusion for high-field MRI scanners with minimal image artifacts.

  13. Balanced Steady State Free Precession for Arterial Spin Labeling MRI: Initial Experience for Blood Flow Mapping in Human Brain, Retina, and Kidney

    PubMed Central

    Park, Sung-Hong; Wang, Danny J.J.; Duong, Timothy Q.

    2013-01-01

    We implemented pseudo-continuous ASL (pCASL) with 2D and 3D balanced steady state free precession (bSSFP) readout for mapping blood flow in the human brain, retina, and kidney, free of distortion and signal dropout, which are typically observed in the most commonly used echo-planar imaging acquisition. High resolution functional brain imaging in the human visual cortex was feasible with 3D bSSFP pCASL. Blood flow of the human retina could be imaged with pCASL and bSSFP in conjunction with a phase cycling approach to suppress the banding artifacts associated with bSSFP. Furthermore, bSSFP based pCASL enabled us to map renal blood flow within a single breath hold. Control and test-retest experiments suggested that the measured blood flow values in retina and kidney were reliable. Because there is no specific imaging tool for mapping human retina blood flow and the standard contrast agent technique for mapping renal blood flow can cause problems for patients with kidney dysfunction, bSSFP based pCASL may provide a useful tool for the diagnosis of retinal and renal diseases and can complement existing imaging techniques. PMID:23664680

  14. Patient-Specific Detection of Cerebral Blood Flow Alterations as Assessed by Arterial Spin Labeling in Drug-Resistant Epileptic Patients

    PubMed Central

    Boscolo Galazzo, Ilaria; Storti, Silvia Francesca; Del Felice, Alessandra; Pizzini, Francesca Benedetta; Arcaro, Chiara; Formaggio, Emanuela; Mai, Roberto; Chappell, Michael; Beltramello, Alberto; Manganotti, Paolo

    2015-01-01

    Electrophysiological and hemodynamic data can be integrated to accurately and precisely identify the generators of abnormal electrical activity in drug-resistant focal epilepsy. Arterial Spin Labeling (ASL), a magnetic resonance imaging (MRI) technique for quantitative noninvasive measurement of cerebral blood flow (CBF), can provide a direct measure of variations in cerebral perfusion associated with the epileptic focus. In this study, we aimed to confirm the ASL diagnostic value in the identification of the epileptogenic zone, as compared to electrical source imaging (ESI) results, and to apply a template-based approach to depict statistically significant CBF alterations. Standard video-electroencephalography (EEG), high-density EEG, and ASL were performed to identify clinical seizure semiology and noninvasively localize the epileptic focus in 12 drug-resistant focal epilepsy patients. The same ASL protocol was applied to a control group of 17 healthy volunteers from which a normal perfusion template was constructed using a mixed-effect approach. CBF maps of each patient were then statistically compared to the reference template to identify perfusion alterations. Significant hypo- and hyperperfused areas were identified in all cases, showing good agreement between ASL and ESI results. Interictal hypoperfusion was observed at the site of the seizure in 10/12 patients and early postictal hyperperfusion in 2/12. The epileptic focus was correctly identified within the surgical resection margins in the 5 patients who underwent lobectomy, all of which had good postsurgical outcomes. The combined use of ESI and ASL can aid in the noninvasive evaluation of drug-resistant epileptic patients. PMID:25946055

  15. Origins of intersubject variability of blood oxygenation level dependent and arterial spin labeling fMRI: implications for quantification of brain activity.

    PubMed

    Gaxiola-Valdez, Ismael; Goodyear, Bradley G

    2012-12-01

    Accurate localization of brain activity using blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) has been challenged because of the large BOLD signal within distal veins. Arterial spin labeling (ASL) techniques offer greater sensitivity to the microvasculature but possess low temporal resolution and limited brain coverage. In this study, we show that the physiological origins of BOLD and ASL depend on whether percent change or statistical significance is being considered. For BOLD and ASL fMRI data collected during a simple unilateral hand movement task, we found that in the area of the contralateral motor cortex the centre of gravity (CoG) of the intersubject coefficient of variation (CV) of BOLD fMRI was near the brain surface for percent change in signal, whereas the CoG of the intersubject CV for Z-score was in close proximity of sites of brain activity for both BOLD and ASL. These findings suggest that intersubject variability of BOLD percent change is vascular in origin, whereas the origin of inter-subject variability of Z-score is neuronal for both BOLD and ASL. For longer duration tasks (12 s or greater), however, there was a significant correlation between BOLD and ASL percent change, which was not evident for short duration tasks (6 s). These findings suggest that analyses directly comparing percent change in BOLD signal between pre-defined regions of interest using short duration stimuli, as for example in event-related designs, may be heavily weighted by large-vessel responses rather than neuronal responses.

  16. OP04QUANTITATIVE MEASUREMENT OF BLOOD FLOW IN PAEDIATRIC BRAIN TUMOURS - A COMPARATIVE STUDY OF DYNAMIC SUSCEPTIBILITY CONTRAST AND MULTI-TIMEPOINT ARTERIAL SPIN LABEL IMAGING

    PubMed Central

    Abernethy, L.J.; Vidyasagar, R.; Pizer, B.L.; Mallucci, C.L.; Avula, S.; Parkes, L.M.

    2014-01-01

    INTRODUCTION: Arterial spin labeling (ASL) is a MR technique that allows for noninvasive quantification of cerebral blood flow (CBF). This technique, predominately used in research, has seen significant technical developments in the last few years that have led to more clinical applications. Currently, the main MR method used to provide perfusion measures in brain tumours is dynamic susceptibility contrast (DSC). DSC traces the signal changes caused by the transit of a bolus of gadolinium contrast agent. ASL has the advantage of not requiring bolus injection of contrast. We have performed a comparative study of DSC and multi-timepoint ASL in paediatric brain tumours (PBT). METHOD: Data from a total of 19 PBT patients (mean age: 9 ± 5 years; 10 females, 9 males) were included in the analyses for this study. Data used were from first presentation scans performed before any surgical intervention. Comparisons of the quantitative measures of CBF and blood arrival time between the two techniques were carried out to test the feasibility of ASL to provide useful quantification measures of CBF in PBT. RESULTS: DSC measurements of tumour blood flow showed a significant decrease in flow in comparison with normal brain, but this is not seen with ASL. There was a strong correlation between ASL and DSC measures of blood flow in normal brain (r = 0.65, p = 0.009), but not in tumour blood flow (r = 0.33, p = 0.2). CONCLUSION: This study demonstrates the feasibility and potential utility of ASL as a non-invasive technique for measuring blood flow in PBT. However, there is a discrepancy between ASL and DSC measures, that may be due to leakage of gadolinium contrast, reflecting the abnormal characteristics of tumour blood vessels in PBT.

  17. Interhemispheric Cerebral Blood Flow Balance during Recovery of Motor Hand Function after Ischemic Stroke—A Longitudinal MRI Study Using Arterial Spin Labeling Perfusion

    PubMed Central

    Missimer, John; Schroth, Gerhard; Hess, Christian W.; Sturzenegger, Matthias; Wang, Danny J. J.; Weder, Bruno; Federspiel, Andrea

    2014-01-01

    Background Unilateral ischemic stroke disrupts the well balanced interactions within bilateral cortical networks. Restitution of interhemispheric balance is thought to contribute to post-stroke recovery. Longitudinal measurements of cerebral blood flow (CBF) changes might act as surrogate marker for this process. Objective To quantify longitudinal CBF changes using arterial spin labeling MRI (ASL) and interhemispheric balance within the cortical sensorimotor network and to assess their relationship with motor hand function recovery. Methods Longitudinal CBF data were acquired in 23 patients at 3 and 9 months after cortical sensorimotor stroke and in 20 healthy controls using pulsed ASL. Recovery of grip force and manual dexterity was assessed with tasks requiring power and precision grips. Voxel-based analysis was performed to identify areas of significant CBF change. Region-of-interest analyses were used to quantify the interhemispheric balance across nodes of the cortical sensorimotor network. Results Dexterity was more affected, and recovered at a slower pace than grip force. In patients with successful recovery of dexterous hand function, CBF decreased over time in the contralesional supplementary motor area, paralimbic anterior cingulate cortex and superior precuneus, and interhemispheric balance returned to healthy control levels. In contrast, patients with poor recovery presented with sustained hypoperfusion in the sensorimotor cortices encompassing the ischemic tissue, and CBF remained lateralized to the contralesional hemisphere. Conclusions Sustained perfusion imbalance within the cortical sensorimotor network, as measured with task-unrelated ASL, is associated with poor recovery of dexterous hand function after stroke. CBF at rest might be used to monitor recovery and gain prognostic information. PMID:25191858

  18. Reproducibility of Kidney Perfusion Measurements With Arterial Spin Labeling at 1.5 Tesla MRI Combined With Semiautomatic Segmentation for Differential Cortical and Medullary Assessment

    PubMed Central

    Hammon, Matthias; Janka, Rolf; Siegl, Christian; Seuss, Hannes; Grosso, Roberto; Martirosian, Petros; Schmieder, Roland E.; Uder, Michael; Kistner, Iris

    2016-01-01

    Abstract Magnetic resonance imaging with arterial spin labeling (ASL) is a noninvasive approach to measure organ perfusion. The purpose of this study was to evaluate the reproducibility of ASL kidney perfusion measurements with semiautomatic segmentation, which allows separate quantification of cortical and medullary perfusion. The right kidneys of 14 healthy volunteers were examined 6 times on 2 occasions (3 times at each occasion). There was a 10-minute pause between each examination and a 14-day interval between the 2 occasions. Cortical, medullary, and whole kidney parenchymal perfusion was determined with customized semiautomatic segmentation software. Coefficient of variances (CVs) and intraclass correlations (ICCs) were calculated. Mean whole, cortical, and medullary kidney perfusion was 307.26 ± 25.65, 337.10 ± 34.83, and 279.61 ± 26.73 mL/min/100 g, respectively. On session 1, mean perfusion for the whole kidney, cortex, and medulla was 307.08 ± 26.91, 336.79 ± 36.54, and 279.60 ± 27.81 mL/min/100 g, respectively, and on session 2, 307.45 ± 24.65, 337.41 ± 33.48, and 279.61 ± 25.94 mL/min/100 g, respectively (P > 0.05; R2 = 0.60/0.59/0.54). For whole, cortical, and medullary kidney perfusion, the total ICC/CV were 0.97/3.43 ± 0.86%, 0.97/4.19 ± 1.33%, and 0.96/4.12 ± 1.36%, respectively. Measurements did not differ significantly and showed a very good correlation (P > 0.05; R2 = 0.75/0.76/0.65). ASL kidney measurements combined with operator-independent semiautomatic segmentation revealed high correlation and low variance of cortical, medullary, and whole kidney perfusion. PMID:26986143

  19. The Effects of Acutely Administered 3,4-Methylenedioxymethamphetamine on Spontaneous Brain Function in Healthy Volunteers Measured with Arterial Spin Labeling and Blood Oxygen Level–Dependent Resting State Functional Connectivity

    PubMed Central

    Carhart-Harris, Robin L.; Murphy, Kevin; Leech, Robert; Erritzoe, David; Wall, Matthew B.; Ferguson, Bart; Williams, Luke T.J.; Roseman, Leor; Brugger, Stefan; De Meer, Ineke; Tanner, Mark; Tyacke, Robin; Wolff, Kim; Sethi, Ajun; Bloomfield, Michael A.P.; Williams, Tim M.; Bolstridge, Mark; Stewart, Lorna; Morgan, Celia; Newbould, Rexford D.; Feilding, Amanda; Curran, H. Val; Nutt, David J.

    2015-01-01

    Background The compound 3,4-methylenedioxymethamphetamine (MDMA) is a potent monoamine releaser that produces an acute euphoria in most individuals. Methods In a double-blind, placebo-controlled, balanced-order study, MDMA was orally administered to 25 physically and mentally healthy individuals. Arterial spin labeling and seed-based resting state functional connectivity (RSFC) were used to produce spatial maps displaying changes in cerebral blood flow (CBF) and RSFC after MDMA administration. Participants underwent two arterial spin labeling and two blood oxygen level–dependent scans in a 90-minute scan session; MDMA and placebo study days were separated by 1 week. Results Marked increases in positive mood were produced by MDMA. Decreased CBF only was observed after MDMA, and this was localized to the right medial temporal lobe (MTL), thalamus, inferior visual cortex, and the somatosensory cortex. Decreased CBF in the right amygdala and hippocampus correlated with ratings of the intensity of global subjective effects of MDMA. The RSFC results complemented the CBF results, with decreases in RSFC between midline cortical regions, the medial prefrontal cortex, and MTL regions, and increases between the amygdala and hippocampus. There were trend-level correlations between these effects and ratings of intense and positive subjective effects. Conclusions The MTLs appear to be specifically implicated in the mechanism of action of MDMA, but further work is required to elucidate how the drug’s characteristic subjective effects arise from its modulation of spontaneous brain activity. PMID:24495461

  20. Spin foams without spins

    NASA Astrophysics Data System (ADS)

    Hnybida, Jeff

    2016-10-01

    We formulate the spin foam representation of discrete SU(2) gauge theory as a product of vertex amplitudes each of which is the spin network generating function of the boundary graph dual to the vertex. In doing so the sums over spins have been carried out. The boundary data of each n-valent node is explicitly reduced with respect to the local gauge invariance and has a manifest geometrical interpretation as a framed polyhedron of fixed total area. Ultimately, sums over spins are traded for contour integrals over simple poles and recoupling theory is avoided using generating functions.

  1. Positron emission tomography/magnetic resonance hybrid scanner imaging of cerebral blood flow using 15O-water positron emission tomography and arterial spin labeling magnetic resonance imaging in newborn piglets

    PubMed Central

    Andersen, Julie B; Henning, William S; Lindberg, Ulrich; Ladefoged, Claes N; Højgaard, Liselotte; Greisen, Gorm; Law, Ian

    2015-01-01

    Abnormality in cerebral blood flow (CBF) distribution can lead to hypoxic–ischemic cerebral damage in newborn infants. The aim of the study was to investigate minimally invasive approaches to measure CBF by comparing simultaneous 15O-water positron emission tomography (PET) and single TI pulsed arterial spin labeling (ASL) magnetic resonance imaging (MR) on a hybrid PET/MR in seven newborn piglets. Positron emission tomography was performed with IV injections of 20 MBq and 100 MBq 15O-water to confirm CBF reliability at low activity. Cerebral blood flow was quantified using a one-tissue-compartment-model using two input functions: an arterial input function (AIF) or an image-derived input function (IDIF). The mean global CBF (95% CI) PET-AIF, PET-IDIF, and ASL at baseline were 27 (23; 32), 34 (31; 37), and 27 (22; 32) mL/100 g per minute, respectively. At acetazolamide stimulus, PET-AIF, PET-IDIF, and ASL were 64 (55; 74), 76 (70; 83) and 79 (67; 92) mL/100 g per minute, respectively. At baseline, differences between PET-AIF, PET-IDIF, and ASL were 22% (P<0.0001) and −0.7% (P=0.9). At acetazolamide, differences between PET-AIF, PET-IDIF, and ASL were 19% (P=0.001) and 24% (P=0.0003). In conclusion, PET-IDIF overestimated CBF. Injected activity of 20 MBq 15O-water had acceptable concordance with 100 MBq, without compromising image quality. Single TI ASL was questionable for regional CBF measurements. Global ASL CBF and PET CBF were congruent during baseline but not during hyperperfusion. PMID:26058699

  2. Acute arterial occlusion - kidney

    MedlinePlus

    Acute renal arterial thrombosis; Renal artery embolism; Acute renal artery occlusion; Embolism - renal artery ... main artery to the kidney is called the renal artery. Reduced blood flow through the renal artery ...

  3. Glial fibrillary acidic protein (GFAP) immunoreactivity correlates with cortical perfusion parameters determined by bolus tracking arterial spin labelling (bt-ASL) magnetic resonance (MR) imaging in the Wistar Kyoto rat.

    PubMed

    Gormley, Shane; Rouine, Jennifer; McIntosh, Allison; Kerskens, Christian; Harkin, Andrew

    2016-06-01

    Alterations in astrocyte number and function have been implicated in the pathophysiology of a number of psychiatric disorders. The development of magnetic resonance imaging (MRI) as a tool in the animal laboratory has enabled an investigation of the relationship between pathological and neuroimaging markers in animal models. However the physiological processes which underlie these markers and their role in mediating behavioural deficits is still poorly understood. Rodent models have provided us with important insights into physiological and cellular mechanisms which may mediate anxiety and depression-related behaviours. The Wistar-Kyoto (WKY) rat is a strain which endogenously expresses highly anxious and depressive-like behaviours and has previously been reported to exhibit alterations in immunoreactivity for the astrocytic marker glial fibrillary acidic protein (GFAP) in brain sub-regions relative to more stress resilient out-bred strains. Here we report that the depressive and anxiety-like behaviours exhibited by the WKY rat strain are associated with alterations in brain morphology including a decrease in hippocampal volume, coupled with reduced resting state frontal cortical perfusion as assessed by MR bolus tracking arterial spin labelling (bt-ASL) relative to the out-bred Wistar strain. Pre-limbic cortical GFAP immunoreactivity and astrocyte cell number were positively correlated with cortical blood perfusion in the WKY strain. These experiments provide a link between pathological and neuroimaging markers of aberrant astrocytic function and add validity to the WKY rat as a model for co-morbid anxiety and depression.

  4. Arterial Catheterization

    MedlinePlus

    ... rial line can provide valuable information to adjust oxygen therapy or mechanical ventilator (respirator; breathing machine) settings. The blood oxygen pres- sure measures from an arterial line give ...

  5. Geometrical spin symmetry and spin

    SciTech Connect

    Pestov, I. B.

    2011-07-15

    Unification of General Theory of Relativity and Quantum Mechanics leads to General Quantum Mechanics which includes into itself spindynamics as a theory of spin phenomena. The key concepts of spindynamics are geometrical spin symmetry and the spin field (space of defining representation of spin symmetry). The essence of spin is the bipolar structure of geometrical spin symmetry induced by the gravitational potential. The bipolar structure provides a natural derivation of the equations of spindynamics. Spindynamics involves all phenomena connected with spin and provides new understanding of the strong interaction.

  6. Mesenteric artery ischemia

    MedlinePlus

    ... bowel - mesenteric; Dead gut - mesenteric; Atherosclerosis - mesenteric artery; Hardening of the arteries - mesenteric artery ... the aorta, the main artery from the heart. Hardening of the arteries occurs when fat, cholesterol, and ...

  7. Arterial Stiffness

    PubMed Central

    Avolio, Alberto

    2013-01-01

    Stiffness of large arteries has been long recognized as a significant determinant of pulse pressure. However, it is only in recent decades, with the accumulation of longitudinal data from large and varied epidemiological studies of morbidity and mortality associated with cardiovascular disease, that it has emerged as an independent predictor of cardiovascular risk. This has generated substantial interest in investigations related to intrinsic causative and associated factors responsible for the alteration of mechanical properties of the arterial wall, with the aim to uncover specific pathways that could be interrogated to prevent or reverse arterial stiffening. Much has been written on the haemodynamic relevance of arterial stiffness in terms of the quantification of pulsatile relationships of blood pressure and flow in conduit arteries. Indeed, much of this early work regarded blood vessels as passive elastic conduits, with the endothelial layer considered as an inactive lining of the lumen and as an interface to flowing blood. However, recent advances in molecular biology and increased technological sophistication for the detection of low concentrations of biochemical compounds have elucidated the highly important regulatory role of the endothelial cell affecting vascular function. These techniques have enabled research into the interaction of the underlying passive mechanical properties of the arterial wall with the active cellular and molecular processes that regulate the local environment of the load-bearing components. This review addresses these emerging concepts. PMID:26587425

  8. Carotid artery surgery

    MedlinePlus

    Carotid endarterectomy; CAS surgery; Carotid artery stenosis - surgery; Endarterectomy - carotid artery ... through the catheter around the blocked area during surgery. Your carotid artery is opened. The surgeon removes ...

  9. Angioplasty and stent placement -- peripheral arteries

    MedlinePlus

    Percutaneous transluminal angioplasty - peripheral artery; PTA - peripheral artery; Angioplasty - peripheral arteries; Iliac artery -angioplasty; Femoral artery - angioplasty; Popliteal artery - angioplasty; Tibial artery - angioplasty; ...

  10. Hardening of the arteries

    MedlinePlus

    Atherosclerosis; Arteriosclerosis; Plaque buildup - arteries; Hyperlipidemia - atherosclerosis; Cholesterol - atherosclerosis ... Hardening of the arteries often occurs with aging. As you grow older, ... narrows your arteries and makes them stiffer. These changes ...

  11. Peripheral arterial line (image)

    MedlinePlus

    A peripheral arterial line is a small, short plastic catheter placed through the skin into an artery of the arm or leg. The purpose of a peripheral arterial line is to allow continuous monitoring of ...

  12. Carotid Artery Disease

    MedlinePlus

    ... brain with blood. If you have carotid artery disease, the arteries become narrow, usually because of atherosclerosis. ... one of the causes of stroke. Carotid artery disease often does not cause symptoms, but there are ...

  13. Coronary artery disease

    MedlinePlus Videos and Cool Tools

    The coronary arteries supply blood to the heart muscle itself. Damage to or blockage of a coronary artery can result in injury to the heart. Normally, blood flows through a coronary artery unimpeded. However, a ...

  14. Spin ejector

    DOEpatents

    Andersen, John A.; Flanigan, John J.; Kindley, Robert J.

    1978-01-01

    The disclosure relates to an apparatus for spin ejecting a body having a flat plate base containing bosses. The apparatus has a base plate and a main ejection shaft extending perpendicularly from the base plate. A compressible cylindrical spring is disposed about the shaft. Bearings are located between the shaft and the spring. A housing containing a helical aperture releasably engages the base plate and surrounds the shaft bearings and the spring. A piston having an aperture follower disposed in the housing aperture is seated on the spring and is guided by the shaft and the aperture. The spring is compressed and when released causes the piston to spin eject the body.

  15. MRI of absent left pulmonary artery.

    PubMed

    Debatin, J F; Moon, R E; Spritzer, C E; MacFall, J; Sostman, H D

    1992-01-01

    Unilateral absence of a pulmonary artery, more accurately referred to as unilateral proximal interruption of a pulmonary artery, is a rare congenital anomaly that may occur as an isolated lesion or in association with other congenital cardiovascular abnormalities. Diagnosis of associated lesions is imperative as early detection and intervention may significantly improve the patient's prognosis. We present the case of an adult patient who had come to our attention after suffering neurological decompression illness related to scuba diving. The patient's cardiopulmonary anatomy was evaluated using MRI gated spin echo, cine, and breath-held fast spoiled recalled echo sequences.

  16. Vapor resistant arteries

    NASA Technical Reports Server (NTRS)

    Shaubach, Robert M. (Inventor); Dussinger, Peter M. (Inventor); Buchko, Matthew T. (Inventor)

    1989-01-01

    A vapor block resistant liquid artery structure for heat pipes. A solid tube artery with openings is encased in the sintered material of a heat pipe wick. The openings are limited to that side of the artery which is most remote from the heat source. The liquid in the artery can thus exit the artery through the openings and wet the sintered sheath, but vapor generated at the heat source is unlikely to move around the solid wall of the artery and reverse its direction in order to penetrate the artery through the openings. An alternate embodiment uses finer pore size wick material to resist vapor entry.

  17. spin pumping occurred under nonlinear spin precession

    NASA Astrophysics Data System (ADS)

    Zhou, Hengan; Fan, Xiaolong; Ma, Li; Zhou, Shiming; Xue, Desheng

    Spin pumping occurs when a pure-spin current is injected into a normal metal thin layer by an adjacent ferromagnetic metal layer undergoing ferromagnetic resonance, which can be understood as the inverse effect of spin torque, and gives access to the physics of magnetization dynamics and damping. An interesting question is that whether spin pumping occurring under nonlinear spin dynamics would differ from linear case. It is known that nonlinear spin dynamics differ distinctly from linear response, a variety of amplitude dependent nonlinear effect would present. It has been found that for spin precession angle above a few degrees, nonlinear damping term would present and dominated the dynamic energy/spin-moment dissipation. Since spin pumping are closely related to the damping process, it is interesting to ask whether the nonlinear damping term could be involved in spin pumping process. We studied the spin pumping effect occurring under nonlinear spin precession. A device which is a Pt/YIG microstrip coupled with coplanar waveguide was used. High power excitation resulted in spin precession entering in a nonlinear regime. Foldover resonance lineshape and nonlinear damping have been observed. Based on those nonlinear effects, we determined the values of the precession cone angles, and the maximum cone angle can reach a values as high as 21.5 degrees. We found that even in nonlinear regime, spin pumping is still linear, which means the nonlinear damping and foldover would not affect spin pumping process.

  18. [Abnormal popliteal arteries].

    PubMed

    Elbaz, C

    1975-01-01

    Arteriopathy restricted to the popliteal artery, except in cases of atheroma, must indicate three of four unusual diagnoses: the trapped popliteal artery and the dessicating haematoma are anatomo-clinical entities that have been identified only relatively recently. The popliteal artery may be trapped by the medial gastrocnomius muscle, round the tendon of which the artery passes (totally or partially). This results in compression of the artery and eventually in thrombosis. Clinically, intermittent claudication is seen that may deteriorate and lead to gangrene of the toes. Arteriography makes it possible to diagnose the condition as the condition as the artery is considerably displaced inwards. Surgical correction is simple: sectioning of the tendon and repositioning of the artery. Dessicating haematoma of the popliteal artery is due essentially to atheroma, associated with medianecrosis. A "egg-timer" stenosis is found by arteriography and this condition also progresses towards thrombosis. Arterial restoration is called for, usually by bridging. PMID:1230799

  19. Cooled artery extension

    NASA Technical Reports Server (NTRS)

    Gernert, Nelson J. (Inventor)

    1990-01-01

    An artery vapor trap. A heat pipe artery is constructed with an extension protruding from the evaporator end of the heat pipe beyond the active area of the evaporator. The vapor migrates into the artery extension because of gravity or liquid displacement, and cooling the extension condenses the vapor to liquid, thus preventing vapor lock in the working portion of the artery by removing vapor from within the active artery. The condensed liquid is then transported back to the evaporator by the capillary action of the artery extension itself or by wick located within the extension.

  20. Coronary Artery Disease

    MedlinePlus

    Coronary artery disease (CAD) is the most common type of heart disease. It is the leading cause of death ... both men and women. CAD happens when the arteries that supply blood to heart muscle become hardened ...

  1. Peripheral Artery Disease (PAD)

    MedlinePlus

    ... changes and medication . View an animation of atherosclerosis Atherosclerosis and PAD Atherosclerosis is a disease in which plaque builds up ... of an artery. PAD is usually caused by atherosclerosis in the peripheral arteries (or outer regions away ...

  2. Coronary artery fistula

    MedlinePlus

    Congenital heart defect - coronary artery fistula; Birth defect heart - coronary artery fistula ... attaches to one of the chambers of the heart (the atrium or ventricle) or another blood vessel ( ...

  3. Occlusive Peripheral Arterial Disease

    MedlinePlus

    ... artery. Such people should seek medical care immediately. Did You Know... When people suddenly develop a painful, ... In This Article Animation 1 Peripheral Arterial Disease Did You Know 1 Did You Know... Figure 1 ...

  4. Carotid Artery Disease

    MedlinePlus

    ... and efficacy continues to be studied in several medical centers. This procedure involves the placement of a small flexible tube (catheter) into an artery from the groin. The catheter is then directed to the neck to reach the carotid artery blockage. A balloon pushes open the artery wall and a stent ( ...

  5. [Upper extremity arterial diseases].

    PubMed

    Becker, F

    2007-02-01

    Compared to lower limb arterial diseases, upper limb arterial diseases look rare, heterogeneous with various etiologies and a rather vague clinical picture, but with a negligible risk of amputation. Almost all types of arterial diseases can be present in the upper limb, but the anatomical and hemodynamic conditions particular to the upper limb often confuse the issue. Thus, atherosclerosis affects mainly the subclavian artery in its proximal segment where the potential of collateral pathway is high making the symptomatic forms not very frequent whereas the prevalence of subclavian artery stenosis or occlusion is relatively high. The clinical examination and the etiologies are discussed according to the clinical, anatomical and hemodynamic context.

  6. Jet pump assisted artery

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A procedure for priming an arterial heat pump is reported; the procedure also has a means for maintaining the pump in a primed state. This concept utilizes a capillary driven jet pump to create the necessary suction to fill the artery. Basically, the jet pump consists of a venturi or nozzle-diffuser type constriction in the vapor passage. The throat of this venturi is connected to the artery. Thus vapor, gas, liquid, or a combination of the above is pumped continuously out of the artery. As a result, the artery is always filled with liquid and an adequate supply of working fluid is provided to the evaporator of the heat pipe.

  7. External artery heat pipe

    NASA Technical Reports Server (NTRS)

    Gernert, Nelson J. (Inventor); Ernst, Donald M. (Inventor); Shaubach, Robert M. (Inventor)

    1989-01-01

    An improved heat pipe with an external artery. The longitudinal slot in the heat pipe wall which interconnects the heat pipe vapor space with the external artery is completely filled with sintered wick material and the wall of the external artery is also covered with sintered wick material. This added wick structure assures that the external artery will continue to feed liquid to the heat pipe evaporator even if a vapor bubble forms within and would otherwise block the liquid transport function of the external artery.

  8. Spin Relaxation and Spin Transport in Graphene

    NASA Astrophysics Data System (ADS)

    Wu, M. W.

    2012-02-01

    In this talk we are going to present our theoretical investigations on spin dynamics of graphene under various conditions based on a fully microscopic kinetic-spin-Bloch-equation approach [1]. We manage to nail down the solo spin relaxation mechanism of graphene in measurements from two leading groups, one in US and one in the Netherland. Many novel effects of the electron-electron Coulomb interaction on spin relaxation in graphene are addressed. Our theory can have nice agreement with experimental data.[4pt] [1] M. W. Wu, J. H. Jiang, and M. Q. Weng, ``Spin dynamics in semiconductors,'' Phys. Rep. 493, 61 (2010).

  9. Spin Liquid Condensate of Spinful Bosons

    NASA Astrophysics Data System (ADS)

    Lian, Biao; Zhang, Shoucheng

    2015-03-01

    We introduce the concept of a bosonic spin liquid condensate (SLC), where spinful bosons in a lattice form a zero-temperature spin disordered charge condensate that preserves the spin rotation symmetry, but breaks the U(1) symmetry due to a spinless order parameter with charge one. It has an energy gap to all the spin excitations. We show that such SLC states can be realized in a system of spin S >= 2 bosons. In particular, we analyze the SLC phase diagram in the spin 2 case using a mean-field variational wave function method. We show there is a direct analogy between the SLC and the resonating-valence-bond (RVB) state. The existence of SLC reveals the possible existence of a more general new class of superfluid phases in a lattice.

  10. Spin-Liquid Condensate of Spinful Bosons

    NASA Astrophysics Data System (ADS)

    Lian, Biao; Zhang, Shoucheng

    2014-08-01

    We introduce the concept of a bosonic spin liquid condensate (SLC), where spinful bosons in a lattice form a zero-temperature spin disordered charge condensate that preserves the spin rotation symmetry, but breaks the U(1) symmetry due to a spinless order parameter with charge one. It has an energy gap to all the spin excitations. We show that such SLC states can be realized in a system of spin S ≥2 bosons. In particular, we analyze the SLC phase diagram in the spin 2 case using a mean-field variational wave function method. We show there is a direct analogy between the SLC and the resonating-valence-bond state.

  11. Ballistic spin resonance.

    PubMed

    Frolov, S M; Lüscher, S; Yu, W; Ren, Y; Folk, J A; Wegscheider, W

    2009-04-16

    The phenomenon of spin resonance has had far-reaching influence since its discovery 70 years ago. Electron spin resonance driven by high-frequency magnetic fields has enhanced our understanding of quantum mechanics, and finds application in fields as diverse as medicine and quantum information. Spin resonance can also be induced by high-frequency electric fields in materials with a spin-orbit interaction; the oscillation of the electrons creates a momentum-dependent effective magnetic field acting on the electron spin. Here we report electron spin resonance due to a spin-orbit interaction that does not require external driving fields. The effect, which we term ballistic spin resonance, is driven by the free motion of electrons that bounce at frequencies of tens of gigahertz in micrometre-scale channels of a two-dimensional electron gas. This is a frequency range that is experimentally challenging to access in spin resonance, and especially difficult on a chip. The resonance is manifest in electrical measurements of pure spin currents-we see a strong suppression of spin relaxation length when the oscillating spin-orbit field is in resonance with spin precession in a static magnetic field. These findings illustrate how the spin-orbit interaction can be harnessed for spin manipulation in a spintronic circuit, and point the way to gate-tunable coherent spin rotations in ballistic nanostructures without external alternating current fields. PMID:19370029

  12. RHIC SPIN FLIPPER

    SciTech Connect

    BAI,M.; ROSER, T.

    2007-06-25

    This paper proposes a new design of spin flipper for RHIC to obtain full spin flip with the spin tune staying at half integer. The traditional technique of using an rf dipole or solenoid as spin flipper to achieve full spin flip in the presence of full Siberian snake requires one to change the snake configuration to move the spin tune away from half integer. This is not practical for an operational high energy polarized proton collider like RHIC where beam lifetime is sensitive to small betatron tune change. The design of the new spin flipper as well as numerical simulations are presented.

  13. Magnons, Spin Current and Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Maekawa, Sadamichi

    2012-02-01

    When metals and semiconductors are placed in a temperature gradient, the electric voltage is generated. This mechanism to convert heat into electricity, the so-called Seebeck effect, has attracted much attention recently as the mechanism for utilizing wasted heat energy. [1]. Ferromagnetic insulators are good conductors of spin current, i.e., the flow of electron spins [2]. When they are placed in a temperature gradient, generated are magnons, spin current and the spin voltage [3], i.e., spin accumulation. Once the spin voltage is converted into the electric voltage by inverse spin Hall effect in attached metal films such as Pt, the electric voltage is obtained from heat energy [4-5]. This is called the spin Seebeck effect. Here, we present the linear-response theory of spin Seebeck effect based on the fluctuation-dissipation theorem [6-8] and discuss a variety of the devices. [4pt] [1] S. Maekawa et al, Physics of Transition Metal Oxides (Springer, 2004). [0pt] [2] S. Maekawa: Nature Materials 8, 777 (2009). [0pt] [3] Concept in Spin Electronics, eds. S. Maekawa (Oxford University Press, 2006). [0pt] [4] K. Uchida et al., Nature 455, 778 (2008). [0pt] [5] K. Uchida et al., Nature Materials 9, 894 (2010) [0pt] [6] H. Adachi et al., APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011). [0pt] [7] J. Ohe et al., Phys. Rev. B (2011) [0pt] [8] K. Uchida et al., Appl. Phys. Lett. 97, 104419 (2010).

  14. Bilateral accessory thoracodorsal artery.

    PubMed

    Natsis, Konstantinos; Totlis, Trifon; Tsikaras, Prokopios; Skandalakis, Panagiotis

    2006-09-01

    The subscapular artery arises from the third part of the axillary artery and gives off the circumflex scapular and the thoracodorsal arteries. Although anatomical variations of the axillary artery are very common, the existence of a unilateral accessory thoracodorsal artery has been described in the literature only once. There are no reports of bilateral accessory thoracodorsal artery, in the literature. In the present study, a bilateral accessory thoracodorsal artery, originating on either side of the third part of the axillary artery, is described in a 68-year-old female cadaver. All the other branches of the axillary artery had a typical origin, course, distribution and termination. This extremely rare anatomical variation apart from the anatomical importance also has clinical significance for surgeons in this area. Especially, during the dissection or mobilization of the latissimus dorsi that is partly used for coverage problems in many regions of the body and also in dynamic cardiomyoplasty, any iatrogenic injury of this accessory artery may result in ischemia and functional loss of the graft.

  15. Angioplasty and stent placement - peripheral arteries - discharge

    MedlinePlus

    Percutaneous transluminal angioplasty - peripheral artery - discharge; PTA - peripheral artery - discharge; Angioplasty - peripheral artery - discharge; Balloon angioplasty - peripheral artery- discharge; PAD - PTA discharge; PVD - ...

  16. Spin Hall effect devices.

    PubMed

    Jungwirth, Tomas; Wunderlich, Jörg; Olejník, Kamil

    2012-05-01

    The spin Hall effect is a relativistic spin-orbit coupling phenomenon that can be used to electrically generate or detect spin currents in non-magnetic systems. Here we review the experimental results that, since the first experimental observation of the spin Hall effect less than 10 years ago, have established the basic physical understanding of the phenomenon, and the role that several of the spin Hall devices have had in the demonstration of spintronic functionalities and physical phenomena. We have attempted to organize the experiments in a chronological order, while simultaneously dividing the Review into sections on semiconductor or metal spin Hall devices, and on optical or electrical spin Hall experiments. The spin Hall device studies are placed in a broader context of the field of spin injection, manipulation, and detection in non-magnetic conductors.

  17. Spin Rotation of Formalism for Spin Tracking

    SciTech Connect

    Luccio,A.

    2008-02-01

    The problem of which coefficients are adequate to correctly represent the spin rotation in vector spin tracking for polarized proton and deuteron beams in synchrotrons is here re-examined in the light of recent discussions. The main aim of this note is to show where some previous erroneous results originated and how to code spin rotation in a tracking code. Some analysis of a recent experiment is presented that confirm the correctness of the assumptions.

  18. Superior mesenteric artery syndrome.

    PubMed Central

    Ahmed, A. R.; Taylor, I.

    1997-01-01

    Superior mesenteric artery syndrome is a rare and controversial form of upper intestinal obstruction in which the third part of the duodenum is compressed by the overlying superior mesenteric artery. Any disease process decreasing the angle between the superior mesenteric artery and the abdominal aorta can result in the external compression of the duodenum and subsequent intestinal obstruction. The aetiology, presentation, investigation and management of this unusual condition are discussed. PMID:9497945

  19. [Popliteal artery entrapment syndrome].

    PubMed

    Musumeci, S; Iuppa, A; Beneventano, G; Rinella, P; Mammano, M; Cinquegrani, E

    1986-12-15

    Trapped popliteal artery syndrome is relatively uncommon: the literature reports some 60 cases. The clinical picture is linked to compression of the popliteal artery by the gastrocnemius as it contracts, thus distorting the arterial route. The result is an interruption in the blood flow distally to the area involved due to stenosis of the blood vessel that is at first functional but becomes organic. PMID:3808379

  20. Buckling instability in arteries.

    PubMed

    Vandiver, Rebecca M

    2015-04-21

    Arteries can become tortuous in response to abnormal growth stimuli, genetic defects and aging. It is suggested that a buckling instability is a mechanism that might lead to artery tortuosity. Here, the buckling instability in arteries is studied by examining asymmetric modes of bifurcation of two-layer cylindrical structures that are residually stressed. These structures are loaded by an axial force, internal pressure and have nonlinear, anisotropic, hyperelastic responses to stresses. Strain-softening and reduced opening angle are shown to lower the critical internal pressure leading to buckling. In addition, the ratio of the media thickness to the adventitia thickness is shown to have a dramatic impact on arterial instability.

  1. The middle suprarenal artery arising from the superior mesenteric artery.

    PubMed

    Honma, Satoru; Kudo, Motoi

    2012-01-01

    We observed a rare case of the middle suprarenal artery branching out from the superior mesenteric artery in a 78-year-old male. This atypical artery enters the right suprarenal gland that was also supplied by the superior and the inferior suprarenal arteries as usual. In embryonic stages, vasculature of the vitelline system and the gonadal system is differentially organized. The superior mesenteric artery has been generally thought to be pure vitelline, since there has been no evidence that the superior mesenteric artery supplies other organs than digestive. We then speculate that the present middle suprarenal artery is a remnant of the embryonic gonadal artery from the superior mesenteric artery, whereas a stem artery to the testis disappeared. Surgeons should take notice of the middle suprarenal artery when operations are conducted around the superior mesenteric artery.

  2. Hemorheological abnormalities in human arterial hypertension

    NASA Astrophysics Data System (ADS)

    Lo Presti, Rosalia; Hopps, Eugenia; Caimi, Gregorio

    2014-05-01

    Blood rheology is impaired in hypertensive patients. The alteration involves blood and plasma viscosity, and the erythrocyte behaviour is often abnormal. The hemorheological pattern appears to be related to some pathophysiological mechanisms of hypertension and to organ damage, in particular left ventricular hypertrophy and myocardial ischemia. Abnormalities have been observed in erythrocyte membrane fluidity, explored by fluorescence spectroscopy and electron spin resonance. This may be relevant for red cell flow in microvessels and oxygen delivery to tissues. Although blood viscosity is not a direct target of antihypertensive therapy, the rheological properties of blood play a role in the pathophysiology of arterial hypertension and its vascular complications.

  3. Measuring How Elastic Arteries Function.

    ERIC Educational Resources Information Center

    DeMont, M. Edwin; MacGillivray, Patrick S.; Davison, Ian G.; McConnell, Colin J.

    1997-01-01

    Describes a procedure used to measure force and pressure in elastic arteries. Discusses the physics of the procedure and recommends the use of bovine arteries. Explains the preparation of the arteries for the procedure. (DDR)

  4. Screening for Carotid Artery Stenosis

    MedlinePlus

    ... Task Force learned about the potential benefits and harms of screening for carotid artery stenosis: Health professionals ... blood flow through the arteries. Potential Benefits and Harms of Carotid Artery Stenosis Screening and Treatment The ...

  5. Spin Transport by Collective Spin Excitations

    NASA Astrophysics Data System (ADS)

    Hammel, P. Chris

    We report studies of angular momentum transport in insulating materials. Our measurements reveal efficient spin pumping from high wavevector k spin waves in thin film Y3Fe5O12 (YIG): spin pumping is independent of wavevector up to k ~ 20 μm-1. Optical detection of YIG FMR by NV centers in diamond reveals a role for spin waves in this insulator-to-insulator spin transfer process. Spin transport is typically suppressed by insulating barriers, but we find that fluctuating antiferromagnetic correlations enable efficient spin transport at nm-scale thicknesses in insulating antiferromagnets, even in the absence of long-range order, and that the spin decay length increases with the strength of the antiferromagnetic correlations. This research is supported by the U.S. DOE through Grants DE-FG02-03ER46054 and DE-SC0001304, by the NSF MRSEC program through Grant No. 1420451 and by the Army Research Office through Grant W911NF0910147.

  6. Spin structure functions

    SciTech Connect

    Jian-ping Chen, Alexandre Deur, Sebastian Kuhn, Zein-eddine Meziani

    2011-06-01

    Spin-dependent observables have been a powerful tool to probe the internal structure of the nucleon and to understand the dynamics of the strong interaction. Experiments involving spin degrees of freedom have often brought out surprises and puzzles. The so-called "spin crisis" in the 1980s revealed the limitation of naive quark-parton models and led to intensive worldwide efforts, both experimental and theoretical, to understand the nucleon spin structure. With high intensity and high polarization of both the electron beam and targets, Jefferson Lab has the world's highest polarized luminosity and the best figure-of-merit for precision spin structure measurements. It has made a strong impact in this subfield of research. This chapter will highlight Jefferson Lab's unique contributions in the measurements of valence quark spin distributions, in the moments of spin structure functions at low to intermediate Q2, and in the transverse spin structure.

  7. Diagnosis of Intracranial Artery Dissection

    PubMed Central

    KANOTO, Masafumi; HOSOYA, Takaaki

    2016-01-01

    Cerebral arterial dissection is defined as a hematoma in the wall of a cervical or an intracranial artery. Cerebral arterial dissection causes arterial stenosis, occlusion, and aneurysm, resulting in acute infarction and hemorrhage. Image analysis by such methods as conventional angiography, computed tomography, magnetic resonance imaging, and so on plays an important role in diagnosing cerebral arterial dissection. In this study, we explore the methods and findings involved in the diagnosis of cerebral arterial dissection. PMID:27180630

  8. Coronary artery stent (image)

    MedlinePlus

    ... with a balloon catheter and expands when the balloon is inflated. The stent is then left there to help keep the artery open. ... with a balloon catheter and expands when the balloon is inflated. The stent is then left there to help keep the artery open.

  9. Arterial Pressure Analog.

    ERIC Educational Resources Information Center

    Heusner, A. A.; Tracy, M. L.

    1980-01-01

    Describes a simple hydraulic analog which allows students to explore some physical aspects of the cardiovascular system and provides them with a means to visualize and conceptualize these basic principles. Simulates the behavior of arterial pressure in response to changes in heart rate, stroke volume, arterial compliance, and peripheral…

  10. Coronary artery disease (image)

    MedlinePlus

    ... through these arteries is critical for the heart. Coronary artery disease usually results from the build-up of fatty material and plaque, a condition called atherosclerosis. As the ... blood to the heart can slow or stop, causing chest pain (stable ...

  11. [Transposition of Great Artery].

    PubMed

    Konuma, Takeshi; Shimpo, Hideto

    2015-07-01

    Transposition of the great artery is one of common congenital cardiac disease resulting cyanosis. Death occurs easily in untreated patients with transposition and intact ventricular septal defect (VSD) in infancy at a few days of age when posterior descending coronary artery (PDA) closed. Since there are 2 parallel circulations, flow from pulmonary to systemic circulation is necessary for systemic oxygenation, and Balloon atrial septostomy or prostaglandin infusion should be performed especially if patient do not have VSD. Although the advent of fetal echocardiography, it is difficult to diagnose the transposition of the great arteries (TGA) as abnormality of great vessels is relatively undistinguishable. The diagnosis of transposition is in itself an indication for surgery, and arterial switch procedure is performed in the case the left ventricle pressure remains more than 2/3 of systemic pressure. Preoperative diagnosis is important as associated anomalies and coronary artery branching patterns are important to decide the operative indication and timing of surgery.

  12. Spinning Eggs and Ballerinas

    ERIC Educational Resources Information Center

    Cross, Rod

    2013-01-01

    Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction…

  13. The Steady Spin

    NASA Technical Reports Server (NTRS)

    Fuchs, Richard; Schmidt, Wilhelm

    1931-01-01

    With the object of further clarifying the problem of spinning, the equilibrium of the forces and moments acting on an airplane is discussed in light of the most recent test data. Convinced that in a spin the flight attitude by only small angles of yaw is more or less completely steady, the study is primarily devoted to an investigation of steady spin with no side slip. At small angles, wholly arbitrary and perfectly steady spins may be forced, depending on the type of control displacements. But at large angles only very steep and only "approaching steady" spins are possible, no matter what the control displacements.

  14. Inverse spin Hall effect by spin injection

    NASA Astrophysics Data System (ADS)

    Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.

    2007-09-01

    Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.

  15. Kagome spin ice

    NASA Astrophysics Data System (ADS)

    Mellado, Paula

    Spin ice in magnetic pyrochlore oxides is a peculiar magnetic state. Like ordinary water ice, these materials are in apparent violation with the third law of thermodynamics, which dictates that the entropy of a system in thermal equilibrium vanishes as its temperature approaches absolute zero. In ice, a "zero-point" entropy is retained down to low temperatures thanks to a high number of low-energy positions of hydrogen ions associated with the Bernal-Fowler ice-rules. Spins in pyrochlore oxides Ho2Ti 2O7 and Dy2Ti2O7 exhibit a similar degeneracy of ground states and thus also have a sizable zero-point entropy. A recent discovery of excitations carrying magnetic charges in pyrochlore spin ice adds another interesting dimension to these magnets. This thesis is devoted to a theoretical study of a two-dimensional version of spin ice whose spins reside on kagome, a lattice of corner-sharing triangles. It covers two aspects of this frustrated classical spin system: the dynamics of artificial spin ice in a network of magnetic nanowires and the thermodynamics of crystalline spin ice. Magnetization dynamics in artificial spin ice is mediated by the emission, propagation and absorption of domain walls in magnetic nanowires. The dynamics shows signs of self-organized behavior such as avalanches. The theoretical model compares favorably to recent experiments. The thermodynamics of the microscopic version of spin ice on kagome is examined through analytical calculations and numerical simulations. The results show that, in addition to the high-temperature paramagnetic phase and the low-temperature phase with magnetic order, spin ice on kagome may have an intermediate phase with fluctuating spins and ordered magnetic charges. This work is concluded with a calculation of the entropy of kagome spin ice at zero temperature when one of the sublattices is pinned by an applied magnetic field and the system breaks up into independent spin chains, a case of dimensional reduction.

  16. [Ultrasound imaging of coronary artery].

    PubMed

    Fuse, Shigeto

    2014-09-01

    Coronary arterial anatomy and the terminology were reviewed. There is a specific portion of coronary artery aneurysm in Kawasaki disease. To investigate coronary arterial lesion, ultrasound imaging is useful because of non-invasive, high special and time resolu tion method. I explained the patient posture, the approaching method to the coronary arter ies, ultrasound setting, measurement of coronary arterial diameter and diastolic measurement.

  17. Peripheral artery disease - legs

    MedlinePlus

    ... legs; Arterial insufficiency of the legs; Recurrent leg pain and cramping; Calf pain with exercise ... The main symptoms of PAD are pain, achiness, fatigue, burning, or ... or thighs. These symptoms most often appear during walking or ...

  18. Peripheral Arterial Disease

    MedlinePlus

    ... Prevention Living With Clinical Trials Links Related Topics Atherosclerosis Coronary Heart Disease Heart Attack Smoking and Your ... in the body's arteries, the condition is called atherosclerosis . Over time, plaque can harden and narrow the ...

  19. Coronary artery anomalies.

    PubMed

    Earls, James P

    2006-12-01

    Coronary artery anomalies are uncommon findings but can be of significant clinical importance in a small number of individuals. Clinical presentation depends on the specific anomaly. Most coronary artery anomalies are benign and clinically insignificant, however, some anomalies are potentially significant and can lead to heart failure and even death. Noninvasive imaging has emerged as the preferred way to image coronary anomalies. Both electron beam computed tomography (EBCT) and magnetic resonance angiography (MRA) are useful for the diagnosis of anomalous coronary arteries. Recently, MDCT has also proven to be very useful in the detection and characterization of anomalous coronary arteries. This chapter will review the appearance of the most commonly encountered coronary anomalies on MDCT. PMID:17709086

  20. Renal arteries (image)

    MedlinePlus

    A renal angiogram is a test used to examine the blood vessels of the kidneys. The test is performed ... main vessel of the pelvis, up to the renal artery that leads into the kidney. Contrast medium ...

  1. Peripheral Arterial Disease

    MedlinePlus

    Peripheral arterial disease (PAD) happens when there is a narrowing of the blood vessels outside of your heart. The cause of ... smoking. Other risk factors include older age and diseases like diabetes, high blood cholesterol, high blood pressure, ...

  2. Coronary Artery Bypass Surgery

    MedlinePlus

    ... t help, you may need coronary artery bypass surgery. The surgery creates a new path for blood to flow ... more than one bypass. The results of the surgery usually are excellent. Many people remain symptom-free ...

  3. Retinal artery occlusion

    MedlinePlus

    ... eds. Textbook of Family Medicine . 9th ed. Philadelphia, PA: Elsevier; 2016:chap 17. Duker JS. Retinal arterial ... M, Duker JS, eds. Ophthalmology. 4th ed. Philadelphia, PA: Elsevier; 2014:chap 6.18. Reiss GR, Sipperley ...

  4. Coronary Artery Disease

    MedlinePlus

    ... ve started to help the medicine work. Other Organizations American Heart Association Questions to Ask Your Doctor Am I at risk for coronary artery disease (CAD)? What lifestyle changes should I make to decrease my risk of ...

  5. Spin accumulation in the extrinsic spin Hall effect

    NASA Astrophysics Data System (ADS)

    Tse, Wang-Kong; Fabian, J.; Žutić, I.; Das Sarma, S.

    2005-12-01

    The drift-diffusion formalism for spin-polarized carrier transport in semiconductors is generalized to include spin-orbit coupling. The theory is applied to treat the extrinsic spin Hall effect using realistic boundary conditions. It is shown that carrier and spin-diffusion lengths are modified by the presence of spin-orbit coupling and that spin accumulation due to the extrinsic spin Hall effect is strongly and qualitatively influenced by boundary conditions. Analytical formulas for the spin-dependent carrier recombination rates and inhomogeneous spin densities and currents are presented.

  6. Spin Hall effects

    NASA Astrophysics Data System (ADS)

    Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

    2015-10-01

    Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

  7. Spin caloritronics in graphene

    SciTech Connect

    Ghosh, Angsula; Frota, H. O.

    2015-06-14

    Spin caloritronics, the combination of spintronics with thermoelectrics, exploiting both the intrinsic spin of the electron and its associated magnetic moment in addition to its fundamental electronic charge and temperature, is an emerging technology mainly in the development of low-power-consumption technology. In this work, we study the thermoelectric properties of a Rashba dot attached to two single layer/bilayer graphene sheets as leads. The temperature difference on the two graphene leads induces a spin current, which depends on the temperature and chemical potential. We demonstrate that the Rashba dot behaves as a spin filter for selected values of the chemical potential and is able to filter electrons by their spin orientation. The spin thermopower has also been studied where the effects of the chemical potential, temperature, and also the Rashba term have been observed.

  8. Spin caloritronics in graphene

    NASA Astrophysics Data System (ADS)

    Frota, H. O.; Ghosh, Angsula

    2014-08-01

    Spin caloritronics, the combination of spintronics with thermoelectrics, based on spin and heat transport has attracted a great attention mainly in the development of low-power-consumption technology. In this work we study the thermoelectric properties of a quantum dot attached to two single layer graphene sheets as leads. The temperature difference on the two graphene leads induces a spin current which depends on the temperature and chemical potential. We demonstrate that the quantum dot behaves as a spin filter for selected values of the chemical potential and is able to filter electrons by their spin orientation. The spin thermopower has also been studied where the effects of the chemical potential, temperature and also the Coulomb repulsion due to the double occupancy of an energy level have been observed.

  9. Picosecond Spin Caloritronics

    NASA Astrophysics Data System (ADS)

    Cahill, David G.

    The coupling of spin and heat, i.e., spin caloritronics, gives rise to new physical phenomena in nanoscale spin devices and new ways to manipulate local magnetization. Our work in this field takes advantage of recent advances in the measurement and understanding of heat transport at the nanoscale using ultrafast lasers. We use a picosecond duration pump laser pulses as a source of heat and picosecond duration probe laser pulses to detect changes in temperature, spin accumulation, and spin transfer torque using a combination of time-domain thermoreflectance and time-resolved magneto-optic Kerr effect Our pump-probe optical methods enable us to change the temperature of ferromagnetic layers on a picosecond time-scale and generate enormous heat fluxes on the order of 100 GW m-2 that persist for ~ 30 ps. Thermally-driven ultrafast demagnetization of a perpendicular ferromagnet leads to spin accumulation in a normal metal and spin transfer torque in an in-plane ferromagnet. The data are well described by models of spin generation and transport based on differences and gradients of thermodynamic parameters. The spin-dependent Seebeck effect of a perpendicular ferromagnetic layer converts a heat current into spin current, which in turn can be used to exert a spin transfer torque (STT) on a second ferromagnetic layer with in-plane magnetization. Using a [Co,Ni] multilayer as the source of spin, an energy fluence of ~ 4 J m-2 creates thermal STT sufficient to induce ~ 1 % tilting of the magnetization of a 2 nm-thick CoFeB layer.

  10. Spin coating apparatus

    DOEpatents

    Torczynski, John R.

    2000-01-01

    A spin coating apparatus requires less cleanroom air flow than prior spin coating apparatus to minimize cleanroom contamination. A shaped exhaust duct from the spin coater maintains process quality while requiring reduced cleanroom air flow. The exhaust duct can decrease in cross section as it extends from the wafer, minimizing eddy formation. The exhaust duct can conform to entrainment streamlines to minimize eddy formation and reduce interprocess contamination at minimal cleanroom air flow rates.

  11. Rockets for spin recovery

    NASA Technical Reports Server (NTRS)

    Whipple, R. D.

    1980-01-01

    The potential effectiveness of rockets as an auxiliary means for an aircraft to effect recovery from spins was investigated. The advances in rocket technology produced by the space effort suggested that currently available systems might obviate many of the problems encountered in earlier rocket systems. A modern fighter configuration known to exhibit a flat spin mode was selected. An analytical study was made of the thrust requirements for a rocket spin recovery system for the subject configuration. These results were then applied to a preliminary systems study of rocket components appropriate to the problem. Subsequent spin tunnel tests were run to evaluate the analytical results.

  12. [Splenic artery aneurysms].

    PubMed

    Colović, R; Davidović, L; Bilanović, D; Krivokapić, Z; Grubor, N; Cvetković, S; Radak, V; Marković, M

    2006-01-01

    Although the third most frequent aneurysm in the abdomen, after aneurysms of the aorta and iliac arteries, and most frequent aneurisms of visceral arteries, splenic artery aneurysms are rare, but not very rare. Thanks to the new imaging techniques, first of all ultrasonography, they have been discovered with increasing frequency. We present a series of 9 splenic artery aneurysms. Seven patients were female and two male of average age 49 years (ranging from 28 to 75 years). The majority of afected women were multiparae, with average 3 children (ranging from 1 to 6). One patient had a subacute rupture, and 2 had ruptures into the splenic vein causing portal hypertension. The spleen was enlarged in 7 out of 9 patients. The average size of aneurysms was 3,2 cm (ranging from 2 to 8 cm). The preoperative diagnosis of splenic artery aneurysm was established in 6 patients while in 3 patients aneurism was accidentally found during other operations, during splenectomy in 2, and during the excision of a retroperitoneal tumour in 1 patient. Aneurysmectomy was carried out in 7 patients, while a ligation of the incoming and outcoming wessels was performed in 2 patients with arteriovenous fistula. Splenectomy was performed in 6 patients, while pancreatic tail resection, cholecystectomy and excision of the retroperitoneal tumor were performed in 3 patients. Additional resection of the abdominal aortic aneurysm with reconstruction of aortoiliac segment was performed in 2 patients. There were no mortality and the postoperative recovery was uneventful in all patients. PMID:16989145

  13. Blood Flow in Arteries

    NASA Astrophysics Data System (ADS)

    Ku, David N.

    Blood flow in arteries is dominated by unsteady flow phenomena. The cardiovascular system is an internal flow loop with multiple branches in which a complex liquid circulates. A nondimensional frequency parameter, the Womersley number, governs the relationship between the unsteady and viscous forces. Normal arterial flow is laminar with secondary flows generated at curves and branches. The arteries are living organs that can adapt to and change with the varying hemodynamic conditions. In certain circumstances, unusual hemodynamic conditions create an abnormal biological response. Velocity profile skewing can create pockets in which the direction of the wall shear stress oscillates. Atherosclerotic disease tends to be localized in these sites and results in a narrowing of the artery lumena stenosis. The stenosis can cause turbulence and reduce flow by means of viscous head losses and flow choking. Very high shear stresses near the throat of the stenosis can activate platelets and thereby induce thrombosis, which can totally block blood flow to the heart or brain. Detection and quantification of stenosis serve as the basis for surgical intervention. In the future, the study of arterial blood flow will lead to the prediction of individual hemodynamic flows in any patient, the development of diagnostic tools to quantify disease, and the design of devices that mimic or alter blood flow. This field is rich with challenging problems in fluid mechanics involving three-dimensional, pulsatile flows at the edge of turbulence.

  14. Effect of spin rotation coupling on spin transport

    SciTech Connect

    Chowdhury, Debashree Basu, B.

    2013-12-15

    We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k{sup →}⋅p{sup →} perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k{sup →}⋅p{sup →} framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied.

  15. Coronary Artery Imaging in Children

    PubMed Central

    2015-01-01

    Coronary artery problems in children usually have a significant impact on both short-term and long-term outcomes. Early and accurate diagnosis, therefore, is crucial but technically challenging due to the small size of the coronary artery, high heart rates, and limited cooperation of children. Coronary artery visibility on CT and MRI in children is considerably improved with recent technical advancements. Consequently, CT and MRI are increasingly used for evaluating various congenital and acquired coronary artery abnormalities in children, such as coronary artery anomalies, aberrant coronary artery anatomy specific to congenital heart disease, Kawasaki disease, Williams syndrome, and cardiac allograft vasculopathy. PMID:25741188

  16. Electron spin susceptibility of superconductors

    SciTech Connect

    Levitov, L.S.; Nazarov, Y.V.; Eliashberg, G.M.

    1985-03-10

    The effect of spin polarization due to the Meissner currents on the electron spin susceptibility of a superconductor is studied. This effect accounts for a susceptibility considerably stronger than that of a normal metal. The spin distribution is discussed.

  17. Understanding Arteries | Coronary Artery Disease | NIH MedlinePlus the Magazine

    MedlinePlus

    ... this page please turn Javascript on. Feature: Coronary Artery Disease Understanding Arteries Past Issues / Fall 2010 Table of Contents Below: ... the arteries and veins are healthy. A Healthy Artery An artery is a muscular tube. It has ...

  18. Spin Waves in Quasiequilibrium Spin Systems

    SciTech Connect

    Bedell, Kevin S.; Dahal, Hari P.

    2006-07-28

    Using the Landau Fermi liquid theory we discovered a new propagating transverse spin wave in a paramagnetic system which is driven slightly out of equilibrium without applying an external magnetic field. We find a gapless mode which describes the uniform precession of the magnetization in the absence of a magnetic field. We also find a gapped mode associated with the precession of the spin current around the internal field. The gapless mode has a quadratic dispersion leading to a T{sup 3/2} contribution to the specific heat. These modes significantly contribute to the dynamic structure function.

  19. Transcatheter Arterial Embolization for Spontaneous Rupture of the Omental Artery

    SciTech Connect

    Matsumoto, Tomohiro; Yamagami, Takuji; Morishita, Hiroyuki; Iida, Shigeharu; Tazoe, Jun; Asai, Shunsuke; Masui, Koji; Ikeda, Jun; Nagata, Akihiro; Sato, Osamu; Nishimura, Tsunehiko

    2011-02-15

    We encountered a rare case of spontaneous rupture of the omental artery. A 25-year-old man without any episode of abdominal trauma or bleeding disorders came to the emergency unit with left upper abdominal pain. Hematoma with extravasation of the greater omentum and a hemoperitoneum was confirmed on abdominal contrast-enhanced computed tomography. Bleeding from the omental artery was suspected based on these findings. Transcatheter arterial embolization was successfully performed after extravasation of the omental artery, which arises from the left gastroepiploic artery, was confirmed on arteriography. Partial ometectomy was performed 10 days after transcatheter arterial embolization, revealing that the hematoma measured 10 cm in diameter in the greater omentum. Pathological examination showed rupture of the branch of an omental artery without abnormal findings, such as an aneurysm or neoplasm. Thus, we diagnosed him with spontaneous rupture of the omental artery. The patient recovered and was discharged from the hospital 10 days after the surgery, with a favorable postoperative course.

  20. Brachial Artery Access for Percutaneous Renal Artery Interventions

    SciTech Connect

    Kaukanen, Erkki T.; Manninen, Hannu I.; Matsi, Pekka J.; Soeder, Heini K.

    1997-09-15

    Purpose: To evaluate the suitability of transbrachial access for endovascular renal artery interventions. Methods: During 37 consecutive endovascular renal artery interventions, the transbrachial approach was used on nine patients (mean age 63 years; range 41-76 years) for 11 renal artery procedures on native kidneys and one percutaneous transluminal angioplasty (PTA) on a transplanted kidney. The reason for using transbrachial access was a steep aorta-renal angle in five, and severe aorta-iliac atherosclerosis in the remaining patients. In addition to the intervention catheter in the left brachial artery, an additional nonselective catheter for controlling the procedure was inserted transfemorally (six patients) or via the contralateral brachial artery. Results: Eleven interventions (six PTAs, five stents) were successfully completed. The one failure resulted from impenetrable subclavian artery stenosis. The only major complication was a brachial artery pseudoaneurysm requiring surgical treatment. Conclusion: Transbrachial access is an effective and relatively safe technique for renal artery interventions when transfemoral access is not possible.

  1. Single spin magnetic resonance

    NASA Astrophysics Data System (ADS)

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.

  2. Spin coating of electrolytes

    DOEpatents

    Stetter, Joseph R.; Maclay, G. Jordan

    1989-01-01

    Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.

  3. Coherent spin-networks

    SciTech Connect

    Bianchi, Eugenio; Magliaro, Elena; Perini, Claudio

    2010-07-15

    In this paper we discuss a proposal of coherent states for loop quantum gravity. These states are labeled by a point in the phase space of general relativity as captured by a spin-network graph. They are defined as the gauge-invariant projection of a product over links of Hall's heat kernels for the cotangent bundle of SU(2). The labels of the state are written in terms of two unit vectors, a spin and an angle for each link of the graph. The heat-kernel time is chosen to be a function of the spin. These labels are the ones used in the spin-foam setting and admit a clear geometric interpretation. Moreover, the set of labels per link can be written as an element of SL(2,C). These states coincide with Thiemann's coherent states with the area operator as complexifier. We study the properties of semiclassicality of these states and show that, for large spins, they reproduce a superposition over spins of spin-networks with nodes labeled by Livine-Speziale coherent intertwiners. Moreover, the weight associated to spins on links turns out to be given by a Gaussian times a phase as originally proposed by Rovelli.

  4. Sparkling and Spinning Words.

    ERIC Educational Resources Information Center

    Carlson, Ruth Kearney

    1964-01-01

    Teachers should foster in children's writing the use of words with "sparkle" and "spin"--"sparkle" implying brightness and vitality, "spin" connoting industry, patience, and painstaking work. By providing creative listening experiences with good children's or adult literature, the teacher can encourage students to broaden their imaginations and…

  5. Single spin magnetic resonance.

    PubMed

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.

  6. Spin-orbit photonics

    NASA Astrophysics Data System (ADS)

    Cardano, Filippo; Marrucci, Lorenzo

    2015-12-01

    Spin-orbit optical phenomena involve the interaction of the photon spin with the light wave propagation and spatial distribution, mediated by suitable optical media. Here we present a short overview of the emerging photonic applications that rely on such effects.

  7. Single-spin CCD

    NASA Astrophysics Data System (ADS)

    Baart, T. A.; Shafiei, M.; Fujita, T.; Reichl, C.; Wegscheider, W.; Vandersypen, L. M. K.

    2016-04-01

    Spin-based electronics or spintronics relies on the ability to store, transport and manipulate electron spin polarization with great precision. In its ultimate limit, information is stored in the spin state of a single electron, at which point quantum information processing also becomes a possibility. Here, we demonstrate the manipulation, transport and readout of individual electron spins in a linear array of three semiconductor quantum dots. First, we demonstrate single-shot readout of three spins with fidelities of 97% on average, using an approach analogous to the operation of a charge-coupled device (CCD). Next, we perform site-selective control of the three spins, thereby writing the content of each pixel of this ‘single-spin charge-coupled device’. Finally, we show that shuttling an electron back and forth in the array hundreds of times, covering a cumulative distance of 80 μm, has negligible influence on its spin projection. Extrapolating these results to the case of much larger arrays points at a diverse range of potential applications, from quantum information to imaging and sensing.

  8. Arterial hypertension and cancer.

    PubMed

    Milan, Alberto; Puglisi, Elisabetta; Ferrari, Laura; Bruno, Giulia; Losano, Isabel; Veglio, Franco

    2014-05-15

    Arterial hypertension and cancer are two of the most important causes of mortality in the world; correlations between these two clinical entities are complex and various. Cancer therapy using old (e.g., mitotic spindle poisons) as well as new (e.g., monoclonal antibody) drugs may cause arterial hypertension through different mechanisms; sometimes the increase of blood pressure levels may be responsible for chemotherapy withdrawal. Among newer cancer therapies, drugs interacting with the VEGF (vascular endothelial growth factors) pathways are the most frequently involved in hypertension development. However, many retrospective studies have suggested a relationship between antihypertensive treatment and risk of cancer, raising vast public concern. The purposes of this brief review have then been to analyse the role of chemotherapy in the pathogenesis of hypertension, to summarize the general rules of arterial hypertension management in this field and finally to evaluate the effects of antihypertensive therapy on cancer disease.

  9. Prominent gastroduodenal artery: Endosonographic sign of celiac artery stenosis

    PubMed Central

    Gonen, Can; Sürmelioğlu, Ali; Tilki, Metin; Kiliçoğlu, Gamze

    2016-01-01

    Celiac artery (CA) stenosis is a relatively common finding in patients undergoing pancreaticoduodenectomy (PD). In the presence of CA stenosis, arterial blood supply to the celiac territory is usually sustained from the superior mesenteric artery (SMA) through well-developed collaterals. In this paper, the authors report endosonographically identified prominent gastroduodenal artery as the sign of CA stenosis for the first time. Uncovering previously unidentified vascular abnormality, endoscopic ultrasound (EUS) has improved patient management. The patient had uneventful collateral preserving PD. PMID:27803908

  10. Spin-labeled polyribonucleotides.

    PubMed Central

    Petrov, A I; Sukhorukov, B I

    1980-01-01

    Poly (U), poly (C) and poly (A) were spin labeled with N-(2,2,5,5-tetramethyl-3-carbonylpyrroline-1-oxyl)-imidazole. This spin label interacts selectively with 2' OH ribose groups of polynucleotides and does not modify the nucleic acid bases. The extent of spin labeling is not dependent upon the nature of the base and is entirely determined by rigidity of the secondary structure of the polynucleotide. The extent of modification for poly (U), poly (C) and poly (A) was 4.2, 1.7 and 1.5 per cent, respectively, the secondary structure of the polynucleotides being practically unchanged. Some physico-chemical properties of the spin-labeled polynucleotides were investigated by ESR spectroscopy. Rotational correlation times of the spin label and activation energy of its motion were calculated. PMID:6253911

  11. Spin-Wave Diode

    NASA Astrophysics Data System (ADS)

    Lan, Jin; Yu, Weichao; Wu, Ruqian; Xiao, Jiang

    2015-10-01

    A diode, a device allowing unidirectional signal transmission, is a fundamental element of logic structures, and it lies at the heart of modern information systems. The spin wave or magnon, representing a collective quasiparticle excitation of the magnetic order in magnetic materials, is a promising candidate for an information carrier for the next-generation energy-saving technologies. Here, we propose a scalable and reprogrammable pure spin-wave logic hardware architecture using domain walls and surface anisotropy stripes as waveguides on a single magnetic wafer. We demonstrate theoretically the design principle of the simplest logic component, a spin-wave diode, utilizing the chiral bound states in a magnetic domain wall with a Dzyaloshinskii-Moriya interaction, and confirm its performance through micromagnetic simulations. Our findings open a new vista for realizing different types of pure spin-wave logic components and finally achieving an energy-efficient and hardware-reprogrammable spin-wave computer.

  12. Fractionalized spin-wave continuum in kagome spin liquids

    NASA Astrophysics Data System (ADS)

    Mei, Jia-Wei; Wen, Xiao-Gang

    Motivated by spin-wave continuum (SWC) observed in recent neutron scattering experiments in Herbertsmithite, we use Gutzwiller-projected wave functions to study dynamic spin structure factor S (q , ω) of spin liquid states on the kagome lattice. Spin-1 excited states in spin liquids are represented by Gutzwiller-projected two-spinon excited wave functions. We investigate three different spin liquid candidates, spinon Fermi-surface spin liquid (FSL), Dirac spin liquid (DSL) and random-flux spin liquid (RSL). FSL and RSL have low energy peaks in S (q , ω) at K points in the extended magnetic Brillouin zone, in contrast to experiments where low energy peaks are found at M points. There is no obviuos contradiction between DSL and neutron scattering measurements. Besides a fractionalized spin (i.e. spin-1/2), spinons in DSL carry a fractionalized crystal momentum which is potentially detectable in SWC in the neutron scattering measurements.

  13. Synchronization of spin-transfer torque oscillators by spin pumping, inverse spin Hall, and spin Hall effects

    SciTech Connect

    Elyasi, Mehrdad; Bhatia, Charanjit S.; Yang, Hyunsoo

    2015-02-14

    We have proposed a method to synchronize multiple spin-transfer torque oscillators based on spin pumping, inverse spin Hall, and spin Hall effects. The proposed oscillator system consists of a series of nano-magnets in junction with a normal metal with high spin-orbit coupling, and an accumulative feedback loop. We conduct simulations to demonstrate the effect of modulated charge currents in the normal metal due to spin pumping from each nano-magnet. We show that the interplay between the spin Hall effect and inverse spin Hall effect results in synchronization of the nano-magnets.

  14. Harvesting the radial artery

    PubMed Central

    Osterday, Robert M.; Brodman, Richard F.

    2013-01-01

    The radial artery (RA) has emerged as an important arterial graft for coronary bypass surgery. With improving five-year patency rates and increasing uptake, great attention has been focused on the optimal conduit harvesting technique. We herein present our approach to RA harvesting. Prerequisites of a successful harvest include adherence to important anatomical landmarks, protection of the sensory innervation to the volar forearm, and meticulous handling of the RA branches. Regardless of the harvesting methodology chosen, adherence to a “no-touch” technique will optimize the patency and durability of the RA conduit. PMID:23977633

  15. About Peripheral Artery Disease (PAD)

    MedlinePlus

    ... changes and medication . View an animation of atherosclerosis Atherosclerosis and PAD Atherosclerosis is a disease in which plaque builds up ... of an artery. PAD is usually caused by atherosclerosis in the peripheral arteries (or outer regions away ...

  16. Peripheral Arterial Disease and Claudication

    MedlinePlus

    ... of fatty deposits inside them. This is called atherosclerosis. If you have PAD, your arms, and more ... also more likely in people who already have atherosclerosis in other arteries, such as the arteries in ...

  17. Anisotropic spin relaxation in graphene.

    PubMed

    Tombros, N; Tanabe, S; Veligura, A; Jozsa, C; Popinciuc, M; Jonkman, H T; van Wees, B J

    2008-07-25

    Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the nonlocal geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field B applied perpendicular to the graphene layer. Fields above 1.5 T force the magnetization direction of the ferromagnetic contacts to align to the field, allowing injection of spins perpendicular to the graphene plane. A comparison of the spin signals at B=0 and B=2 T shows a 20% decrease in spin relaxation time for spins perpendicular to the graphene layer compared to spins parallel to the layer. We analyze the results in terms of the different strengths of the spin-orbit effective fields in the in-plane and out-of-plane directions and discuss the role of the Elliott-Yafet and Dyakonov-Perel mechanisms for spin relaxation. PMID:18764351

  18. Spin-orbit coupling and quantum spin Hall effect for neutral atoms without spin flips.

    PubMed

    Kennedy, Colin J; Siviloglou, Georgios A; Miyake, Hirokazu; Burton, William Cody; Ketterle, Wolfgang

    2013-11-27

    We propose a scheme which realizes spin-orbit coupling and the quantum spin Hall effect for neutral atoms in optical lattices without relying on near resonant laser light to couple different spin states. The spin-orbit coupling is created by modifying the motion of atoms in a spin-dependent way by laser recoil. The spin selectivity is provided by Zeeman shifts created with a magnetic field gradient. Alternatively, a quantum spin Hall Hamiltonian can be created by all-optical means using a period-tripling, spin-dependent superlattice. PMID:24329453

  19. Towards a Compositional SPIN

    NASA Technical Reports Server (NTRS)

    Pasareanu, Corina S.; Giannakopoulou, Dimitra

    2006-01-01

    This paper discusses our initial experience with introducing automated assume-guarantee verification based on learning in the SPIN tool. We believe that compositional verification techniques such as assume-guarantee reasoning could complement the state-reduction techniques that SPIN already supports, thus increasing the size of systems that SPIN can handle. We present a "light-weight" approach to evaluating the benefits of learning-based assume-guarantee reasoning in the context of SPIN: we turn our previous implementation of learning for the LTSA tool into a main program that externally invokes SPIN to provide the model checking-related answers. Despite its performance overheads (which mandate a future implementation within SPIN itself), this approach provides accurate information about the savings in memory. We have experimented with several versions of learning-based assume guarantee reasoning, including a novel heuristic introduced here for generating component assumptions when their environment is unavailable. We illustrate the benefits of learning-based assume-guarantee reasoning in SPIN through the example of a resource arbiter for a spacecraft. Keywords: assume-guarantee reasoning, model checking, learning.

  20. Resonant Tunneling Spin Pump

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2007-01-01

    The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

  1. Uterine artery embolization

    MedlinePlus

    ... the procedure. UAE is less invasive than surgical treatments for uterine fibroids. Many women may return more quickly to activities ... SC, Spies JB, Worthington-Kirsch R, et al. Uterine artery embolization for ... from the FIBROID registry. Obstet Gynecol . 2008; 111:22-33. Munro ...

  2. [Atherosclerotic renal artery stenosis].

    PubMed

    Sauguet, A; Honton, B

    2014-12-01

    Atherosclerotic renal artery stenosis can cause ischaemic nephropathy and arterial hypertension. Renal artery stenosis (RAS) continues to be a problem for clinicians, with no clear consensus on how to investigate and assess the clinical significance of stenotic lesions and manage the findings. RAS caused by fibromuscular dysplasia is probably commoner than previously appreciated, should be actively looked for in younger hypertensive patients and can be managed successfully with angioplasty. Atheromatous RAS is associated with increased incidence of cardiovascular events and increased cardiovascular mortality, and is likely to be seen with increasing frequency. Many patients with RAS may be managed effectively with medical therapy for several years without endovascular stenting, as demonstrated by randomized, prospective trials including the cardiovascular outcomes in Renal Atherosclerotic Lesions (CORAL) trial, the Angioplasty and Stenting for Renal Artery Lesions (ASTRAL) trial. These trials share the limitation of excluding subsets of patients with high-risk clinical presentations, including episodic pulmonary edema and rapidly progressing renal failure and hypertension. Blood pressure control and medication adjustment may become more difficult with declining renal function and may prevent the use of angiotensin receptor blocker and angiotensin-converting enzyme inhibitors. The objective of this review is to evaluate the current management of RAS for cardiologists in the context of recent randomized clinical trials. There is now interest in looking more closely at patient selection for intervention, with focus on intervening only in patients with the highest-risk presentations such as flash pulmonary edema, rapidly declining renal function and severe resistant hypertension. PMID:25450992

  3. Higher spins and holography

    NASA Astrophysics Data System (ADS)

    Kraus, Per; Ross, Simon F.

    2013-05-01

    The principles of quantum mechanics and relativity impose rigid constraints on theories of massless particles with nonzero spin. Indeed, Yang-Mills theory and General Relativity are the unique solution in the case of spin-1 and spin-2. In asymptotically flat spacetime, there are fundamental obstacles to formulating fully consistent interacting theories of particles of spin greater than 2. However, indications are that such theories are just barely possible in asymptotically anti-de Sitter or de Sitter spacetimes, where the non-existence of an S-matrix provides an escape from the theorems restricting theories in Minkowski spacetime. These higher spin gravity theories are therefore of great intrinsic interest, since they, along with supergravity, provide the only known field theories generalizing the local invariance principles of Yang-Mills theory and General Relativity. While work on higher spin gravity goes back several decades, the subject has gained broader appeal in recent years due to its appearance in the AdS/CFT correspondence. In three and four spacetime dimensions, there exist duality proposals linking higher spin gravity theories to specific conformal field theories living in two and three dimensions respectively. The enlarged symmetry algebra of the conformal field theories renders them exactly soluble, which makes them excellent laboratories for understanding in detail the holographic mechanism behind AdS/CFT duality. Steady progress is also being made on better understanding the space of possible higher spin gravity theories and their physical content. This work includes classifying the possible field multiplets and their interactions, constructing exact solutions of the nonlinear field equations, and relating higher spin theories to string theory. A full understanding of these theories will involve coming to grips with the novel symmetry principles that enlarge those of General Relativity and Yang-Mills theory, and one can hope that this will provide

  4. SPINning parallel systems software.

    SciTech Connect

    Matlin, O.S.; Lusk, E.; McCune, W.

    2002-03-15

    We describe our experiences in using Spin to verify parts of the Multi Purpose Daemon (MPD) parallel process management system. MPD is a distributed collection of processes connected by Unix network sockets. MPD is dynamic processes and connections among them are created and destroyed as MPD is initialized, runs user processes, recovers from faults, and terminates. This dynamic nature is easily expressible in the Spin/Promela framework but poses performance and scalability challenges. We present here the results of expressing some of the parallel algorithms of MPD and executing both simulation and verification runs with Spin.

  5. Quantum spin Hall effect.

    PubMed

    Bernevig, B Andrei; Zhang, Shou-Cheng

    2006-03-17

    The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. The existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2(e/4pi). The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.

  6. Quantum Spin Hall Effect

    SciTech Connect

    Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-01-15

    The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.

  7. Spin tracking in RHIC

    SciTech Connect

    Luccio, A.U.; Katayama, T.; Wu, H.

    1997-07-01

    In the acceleration of polarized protons in RHIC many spin depolarizing resonances are encountered. Helical Siberian snakes will be used to overcome depolarizing effects. The behavior of polarization can be studied by numerical tracking in a model accelerator. That allows one to check the strength of the resonances, to study the effect of snakes, to find safe lattice tune regions, and finally to study the operation of special devices like spin flippers. In this paper the authors describe numerical spin tracking. Results show that, for the design corrected distorted orbit and the design beam emittance, the polarization of the beam will be preserved in the whole range of proton energies in RHIC.

  8. Arterial Stiffness Gradient

    PubMed Central

    Fortier, Catherine; Agharazii, Mohsen

    2016-01-01

    Background Aortic stiffness is a strong predictor of cardiovascular mortality in various clinical conditions. The aim of this review is to focus on the arterial stiffness gradient, to discuss the integrated role of medium-sized muscular conduit arteries in the regulation of pulsatile pressure and organ perfusion and to provide a rationale for integrating their mechanical properties into risk prediction. Summary The physiological arterial stiffness gradient results from a higher degree of vascular stiffness as the distance from the heart increases, creating multiple reflective sites and attenuating the pulsatile nature of the forward pressure wave along the arterial tree down to the microcirculation. The stiffness gradient hypothesis simultaneously explains its physiological beneficial effects from both cardiac and peripheral microcirculatory points of view. The loss or reversal of stiffness gradient leads to the transmission of a highly pulsatile pressure wave into the microcirculation. This suggests that a higher degree of stiffness of medium-sized conduit arteries may play a role in protecting the microcirculation from a highly pulsatile forward pressure wave. Using the ratio of carotid-femoral pulse wave velocity (PWV) to carotid-radial PWV, referred to as PWV ratio, a recent study in a dialysis cohort has shown that the PWV ratio is a better predictor of mortality than the classical carotid-femoral PWV. Key Messages Theoretically, the use of the PWV ratio seems more logical for risk determination than aortic stiffness as it provides a better estimation of the loss of stiffness gradient, which is the unifying hypothesis that explains the impact of aortic stiffness both on the myocardium and on peripheral organs. PMID:27195235

  9. Spin pumping and inverse spin Hall effects—Insights for future spin-orbitronics (invited)

    SciTech Connect

    Zhang, Wei Jungfleisch, Matthias B.; Jiang, Wanjun; Fradin, Frank Y.; Pearson, John E.; Hoffmann, Axel; Sklenar, Joseph; Ketterson, John B.

    2015-05-07

    Quantification of spin-charge interconversion has become increasingly important in the fast-developing field of spin-orbitronics. Pure spin current generated by spin pumping acts as a sensitive probe for many bulk and interface spin-orbit effects, which has been indispensable for the discovery of many promising new spin-orbit materials. We apply spin pumping and inverse spin Hall effect experiments, as a useful metrology, and study spin-orbit effects in a variety of metals and metal interfaces. We quantify the spin Hall effects in Ir and W using the conventional bilayer structures and discuss the self-induced voltage in a single layer of ferromagnetic permalloy. Finally, we extend our discussions to multilayer structures and quantitatively reveal the spin current flow in two consecutive normal metal layers.

  10. Spin waves in a persistent spin-current Fermi liquid

    SciTech Connect

    Feldmann, J. D.; Bedell, K. S.

    2010-06-15

    We report two theoretical results for transverse spin waves, which arise in a system with a persistent spin current. Using Fermi liquid theory, we introduce a spin current in the ground state of a polarized or unpolarized Fermi liquid, and we derive the resultant spin waves using the Landau kinetic equation. The resulting spin waves have a q{sup 1} and q{sup 1/2} dispersion to leading order for the polarized and unpolarized systems, respectively.

  11. Spin transfer torques in the nonlocal lateral spin valve.

    PubMed

    Xu, Yuan; Xia, Ke; Ma, Zhongshui

    2008-06-11

    We report a theoretical study on the spin and electron transport in the nonlocal lateral spin valve with a non-collinear magnetic configuration. The nonlocal magnetoresistance, defined as the voltage difference on the detection lead over the injected current, is derived analytically. The spin transfer torques on the detection lead are calculated. It is found that spin transfer torques are symmetrical for parallel and antiparallel magnetic configurations, in contrast to that in a conventional sandwiched spin valve. PMID:21825793

  12. Microscopic studies of nonlocal spin dynamics and spin transport (invited)

    SciTech Connect

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

    2015-05-07

    Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

  13. Pluto's Spinning Moons

    NASA Video Gallery

    Most inner moons in the solar system keep one face pointed toward their central planet; this animation shows that certainly isn’t the case with the small moons of Pluto, which behave like spinning ...

  14. MMS Spin Test

    NASA Video Gallery

    The four Magnetospheric Multiscale observatories all undergo what's called a spin test, to learn how well the spacecraft are balanced. It also provides information on how well the mass properties o...

  15. The spin deep within

    SciTech Connect

    Stackhouse, S.

    2008-10-08

    The electronic configuration of iron impurities in lower-mantle minerals influences their physical properties, but it is not well constrained. New studies suggest that ferrous iron in silicate phases exists mainly in an intermediate spin state.

  16. Itinerant spin ice

    NASA Astrophysics Data System (ADS)

    Udagawa, Masafumi

    2014-03-01

    Spin ice is a prototypical frustrated magnet defined on a pyrochlore lattice. The ground state of spin ice is described by a simple rule called ``ice rule'': out of four spins on a tetrahedron, two spins point inward, while the other two outward. This simple rule is not sufficient to determine the spin configuration uniquely, but it leaves macroscopic degeneracy in the ground state. Despite the macroscopic degeneracy, however, the ground state is not completely disordered, but it exhibits algebraic spatial correlation, which characterizes this state as ``Coulomb phase'' where various exotic properties, such as monopole excitations and unusual magnetic responses are observed. Given the peculiar spatial correlation, it is interesting to ask what happens if itinerant electrons coexist and interact with spin ice. Indeed, this setting is relevant to several metallic Ir pyrochlore oxides, such as Ln2Ir2O7 (Ln=Pr, Nd), where Ir 5d itinerant electrons interact with Ln 4f localized moments. In these compounds, anomalous transport phenomena have been reported, such as non-monotonic magnetic field dependence of Hall conductivity and low-temperature resistivity upturn. To address these issues, we adopt a spin-ice-type Ising Kondo lattice model on a pyrochlore lattice, and solve this model by applying the cluster dynamical mean-field theory and the perturbation expansion in terms of the spin-electron coupling. As a result, we found that (i) the resistivity shows a minimum at a characteristic temperature below which spin ice correlation sets in. Moreover, (ii) the Hall conductivity shows anisotropic and non-monotonic magnetic field dependence due to the scattering from the spatially extended spin scalar chirality incorporated in spin ice manifold. These results give unified understanding to the thermodynamic and transport properties of Ln2Ir2O7 (Ln=Pr, Nd), and give new insights into the role of geometrical frustration in itinerant systems. This work has been done in

  17. Spider Spinning for Dummies

    NASA Astrophysics Data System (ADS)

    Bird, Richard S.

    Spider spinning is a snappy name for the problem of listing the ideals of a totally acyclic poset in such a way that each ideal is computed from its predecessor in constant time. Such an algorithm is said to be loopless. Our aim in these lectures is to show how to calculate a loopless algorithm for spider spinning. The calculation makes use of the fundamental laws of functional programming and the real purpose of the exercise is to show these laws in action.

  18. Spin transport in nanoscale spin valves and magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Patibandla, Sridhar

    Spintronics or electronics that utilizes the spin degree of freedom of a single charge carrier (or an ensemble of charge carriers) to store, process, sense or communicate data and information is a rapidly burgeoning field in electronics. In spintronic devices, information is encoded in the spin polarization of a single carrier (or multiple carriers) and the spin(s) of these carrier(s) are manipulated for device operation. This strategy could lead to devices with low power consumption. This dissertation investigates spin transport in one dimensional and two dimensional semiconductors, with a view to applications in spintronic devices. This dissertation is arranged as follows: Chapter 1 gives a detailed introduction and necessary background to understand aspects of spin injection into a semiconductor from a spin polarized source such as a ferromagnet, and spin polarized electron transport in the semiconductor. Chapter 2 discusses the nanoporous alumina technique that is employed to fabricate nanowires and nanowire spin valves for the investigation of spin transport in 1D semiconductors. Chapter 3 investigates the spin transport in quasi one-dimensional spin valves with germanium spacer layer. These spin valves with 50nm in diameter and 1 mum length were fabricated using the porous alumina technique. Spin transport in nanoscale germanium spin valves was demonstrated and the spin relaxation lengths and the spin relaxation times were calculated. Chapter 4 discusses spin transport studies conducted in bulk high purity germanium with a view to comparing spin relaxation mechanisms in low mobility nanowires and high mobility bulk structures. Lateral spin valve with tunnel injectors were employed in this study and the spin transport measurements were conducted at various temperatures. The spin relaxation rates were measured as a function of temperature which allowed us to distinguish between two different mechanisms---D'yakonov-Perel' and Elliott-Yafet---that dominate spin

  19. Coronary artery fistulas

    PubMed Central

    Said, S.A.M.; Thiadens, A.A.H.J.; Fieren, M.J.C.H.; Meijboom, E.J.; van der Werf, T.; Bennink, G.B.W.E.

    2002-01-01

    The aetiology of congenital coronary artery fistulas remains a challenging issue. Coronary arteries with an anatomically normal origin may, for obscure reasons, terminate abnormally and communicate with different single or multiple cardiac chambers or great vessels. When this occurs, the angiographic morphological appearance may vary greatly from discrete channels to plexiform network of vessels. Coronary arteriovenous fistulas (CAVFs) have neither specific signs nor pathognomonic symptoms; the spectrum of clinical features varies considerably. The clinical presentation of symptomatic cases can include angina pectoris, myocardial infarction, fatigue, dyspnoea, CHF, SBE, ventricular and supraventricular tachyarrhythmias or even sudden cardiac death. CAVFs may, however, be a coincidental finding during diagnostic coronary angiography (CAG). CAG is considered the gold standard for diagnosing and delineating the morphological anatomy and pathway of CAVFs. There are various tailored therapeutic modalities for the wide spectrum of clinical manifestations of CAVFs, including conservative pharmacological strategy, percutaneous transluminal embolisation and surgical ligation. ImagesFigure 1Figure 2Figure 3Figure 4 PMID:25696067

  20. Caliber-Persistent Artery

    PubMed Central

    Costa, Sabrina Araújo Pinho; Ruiz, Marcelo Martinson; Kaba, Shajadi Pardo; Florezi, Giovanna Piacenza; Lemos Júnior, Celso Augusto; Witzel, Andréa Lusvarghi

    2015-01-01

    Caliber-persistent artery (CPLA) of the lip is a common vascular anomaly in which a main arterial branch extends to the surface of the mucous tissue with no reduction in its diameter. It usually manifests as pulsatile papule, is easily misdiagnosed, and is observed more frequently among older people, suggesting that its development may involve a degenerative process associated with aging; CPLA is also characterized by the loss of tone of the adjacent supporting connective tissue. Although the diagnosis is clinical, high-resolution Doppler ultrasound is a useful noninvasive tool for evaluating the lesion. This report describes the case of a 58-year-old male patient who complained of a lesion of the lower lip with bleeding and recurrent ulceration. The patient was successfully treated in our hospital after a diagnosis of CPLA and is currently undergoing a clinical outpatient follow-up with no complaints. PMID:26448884

  1. Spin-current emission governed by nonlinear spin dynamics

    PubMed Central

    Tashiro, Takaharu; Matsuura, Saki; Nomura, Akiyo; Watanabe, Shun; Kang, Keehoon; Sirringhaus, Henning; Ando, Kazuya

    2015-01-01

    Coupling between conduction electrons and localized magnetization is responsible for a variety of phenomena in spintronic devices. This coupling enables to generate spin currents from dynamical magnetization. Due to the nonlinearity of magnetization dynamics, the spin-current emission through the dynamical spin-exchange coupling offers a route for nonlinear generation of spin currents. Here, we demonstrate spin-current emission governed by nonlinear magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current emission from the magnetic insulator is probed by the inverse spin Hall effect, which demonstrates nontrivial temperature and excitation power dependences of the voltage generation. The experimental results reveal that nonlinear magnetization dynamics and enhanced spin-current emission due to magnon scatterings are triggered by decreasing temperature. This result illustrates the crucial role of the nonlinear magnon interactions in the spin-current emission driven by dynamical magnetization, or nonequilibrium magnons, from magnetic insulators. PMID:26472712

  2. Quantifying spin Hall angles from spin pumping: experiments and theory.

    PubMed

    Mosendz, O; Pearson, J E; Fradin, F Y; Bauer, G E W; Bader, S D; Hoffmann, A

    2010-01-29

    Spin Hall effects intermix spin and charge currents even in nonmagnetic materials and, therefore, ultimately may allow the use of spin transport without the need for ferromagnets. We show how spin Hall effects can be quantified by integrating Ni{80}Fe{20}|normal metal (N) bilayers into a coplanar waveguide. A dc spin current in N can be generated by spin pumping in a controllable way by ferromagnetic resonance. The transverse dc voltage detected along the Ni{80}Fe{20}|N has contributions from both the anisotropic magnetoresistance and the spin Hall effect, which can be distinguished by their symmetries. We developed a theory that accounts for both. In this way, we determine the spin Hall angle quantitatively for Pt, Au, and Mo. This approach can readily be adapted to any conducting material with even very small spin Hall angles.

  3. Designing electron spin textures and spin interferometers by shape deformations

    NASA Astrophysics Data System (ADS)

    Ying, Zu-Jian; Gentile, Paola; Ortix, Carmine; Cuoco, Mario

    2016-08-01

    We demonstrate that the spin orientation of an electron propagating in a one-dimensional nanostructure with Rashba spin-orbit (SO) coupling can be manipulated on demand by changing the geometry of the nanosystem. Shape deformations that result in a nonuniform curvature give rise to complex three-dimensional spin textures in space. We employ the paradigmatic example of an elliptically deformed quantum ring to unveil the way to get an all-geometrical and all-electrical control of the spin orientation. The resulting spin textures exhibit a tunable topological character with windings around the radial and the out-of-plane directions. We show that these topologically nontrivial spin patterns affect the spin interference effect in the deformed ring, thereby resulting in different geometry-driven ballistic electronic transport behaviors. Our results establish a deep connection between electronic spin textures, spin transport, and the nanoscale shape of the system.

  4. Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling.

    PubMed

    Caetano, R A

    2016-01-01

    The use of organic materials in spintronic devices has been seriously considered after recent experimental works have shown unexpected spin-dependent electrical properties. The basis for the confection of any spintronic device is ability of selecting the appropriated spin polarization. In this direction, DNA has been pointed out as a potential candidate for spin selection due to the spin-orbit coupling originating from the electric field generated by accumulated electrical charges along the helix. Here, we demonstrate that spin-orbit coupling is the minimum ingredient necessary to promote a spatial spin separation and the generation of spin-current. We show that the up and down spin components have different velocities that give rise to a spin-current. By using a simple situation where spin-orbit coupling is present, we provide qualitative justifications to our results that clearly point to helicoidal molecules as serious candidates to integrate spintronic devices. PMID:27009836

  5. Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling

    PubMed Central

    Caetano, R. A.

    2016-01-01

    The use of organic materials in spintronic devices has been seriously considered after recent experimental works have shown unexpected spin-dependent electrical properties. The basis for the confection of any spintronic device is ability of selecting the appropriated spin polarization. In this direction, DNA has been pointed out as a potential candidate for spin selection due to the spin-orbit coupling originating from the electric field generated by accumulated electrical charges along the helix. Here, we demonstrate that spin-orbit coupling is the minimum ingredient necessary to promote a spatial spin separation and the generation of spin-current. We show that the up and down spin components have different velocities that give rise to a spin-current. By using a simple situation where spin-orbit coupling is present, we provide qualitative justifications to our results that clearly point to helicoidal molecules as serious candidates to integrate spintronic devices. PMID:27009836

  6. LATENT LIFE OF ARTERIES.

    PubMed

    Carrel, A

    1910-07-23

    When a segment of artery, killed by heat, formalin or glycerin is transplanted, it undergoes a rapid degeneration. Its muscle fibers disappear while the tissue of the host reacts by building a new wall of connective tissue. When the transplanted vessel has been preserved in a condition of latent life, no degeneration of the wall occurs, or the wall undergoes only partial degeneration. The muscle fibers can keep their normal appearance, even for a long time after the operation. It is, therefore, demonstrated that arteries can be preserved outside of the body in a condition of unmanifested actual life. The best method of preservation consists of placing the vessels, immersed in vaselin, in an ice box, the temperature of which is slightly above the freezing point. From a surgical standpoint, the transplantation of preserved vessels can be used with some safety. When the arteries were kept in defibrinated blood or vaselin and in cold storage, the proportion of positive results was 75 and 80 per cent., and this can probably be increased. PMID:19867337

  7. Pediatric arterial interventions.

    PubMed

    Marshalleck, Francis

    2010-12-01

    The spectrum of pediatric vascular pathology differs from the adult population and it varies greatly to include congenital and acquired disorders. Although catheter-directed angiography remains the gold standard, most vascular conditions in the child can be adequately diagnosed with magnetic resonance angiography, computed tomographic angiography, or duplex/Doppler ultrasonography with only a few exceptions, such as intrarenal arterial stenosis, small vessel vasculitides, and visceral vascular malformations. The advancement of catheter and wire technology has made it increasingly possible for complex arterial interventions to be performed in children, including embolization, angioplasty with stent insertion, thrombolysis, and endovascular neurological procedures. More angiographic procedures are being performed with the aim of also being therapeutic. Special considerations in children include the use of appropriate equipment and adequate dosing of contrast and of the various medications used during angiography, particularly in patients less than 15 kg in weight. This article will focus on the management of renovascular hypertension, liver transplant hepatic arterial intervention, and the use of carbon dioxide gas as a contrast agent in the child.

  8. Measurements of nuclear spin dynamics by spin-noise spectroscopy

    SciTech Connect

    Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S.; Kavokin, K. V.; Glazov, M. M.; Vladimirova, M.; Scalbert, D.; Cronenberger, S.; Lemaître, A.; Bloch, J.

    2015-06-15

    We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamics in n-GaAs. The SNS experiments were performed on bulk n-type GaAs layers embedded into a high-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation initially prepared by optical pumping is monitored in real time via a shift of the peak position in the electron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauser field acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependent on the electron concentration.

  9. Magnetization plateaux in Bethe ansatz solvable spin-S ladders

    NASA Astrophysics Data System (ADS)

    Maslen, M.; Batchelor, M.; de Gier, J.

    2003-07-01

    We examine the properties of the Bethe ansatz solvable two- and three-leg spin-S ladders. These models include Heisenberg rung interactions of arbitrary strength and thus capture the physics of the spin-S Heisenberg ladders for strong rung coupling. The discrete values derived for the magnetization plateaux are seen to fit with the general prediction based on the Lieb-Schultz-Mattis theorem. We examine the magnetic phase diagram of the spin-1 ladder in detail and find an extended magnetization plateau at the fractional value =1/2 in agreement with the experimental observation for the organic polyradical spin-1 ladder compound BIP-TENO.

  10. Arterial stiffness as a risk factor for coronary artery disease.

    PubMed

    Liao, Josh; Farmer, John

    2014-02-01

    Hypertension is a major modifiable risk factor, and clinical trials have demonstrated that successful reduction of elevated blood pressure to target levels translates into decreased risk for the development of coronary artery disease, stroke, heart failure, and renal failure. The arterial system had previously been regarded as a passive conduit for the transportation of arterial blood to peripheral tissues. The physiologic role the arterial system was greatly expanded by the recognition of the central role of the endothelial function in a variety of physiologic processes. The role of arterial function and structure in cardiovascular physiology was expanded with the development of a variety of parameters that evaluate arterial stiffness. Markers of arterial stiffness have been correlated with cardiovascular outcomes, and have been classified as an emerging risk factor that provides prognostic information beyond standard stratification strategies involving hypertension, diabetes, obesity, dyslipidemia and smoking. Multiple epidemiologic studies have correlated markers of arterial stiffness such as pulse-wave velocity, augmentation index and pulse pressure with risk for the development of fatal and nonfatal cardiovascular events. Additionally, measurements of arterial stiffness had clarified the results of clinical trials that demonstrated differing impacts on clinical outcomes, despite similar reductions in blood pressure, as measured by brachial and sphygmomanometry.

  11. Basic spin physics.

    PubMed

    Pipe, J G

    1999-11-01

    Magnetic resonance imaging is fundamentally a measurement of the magnetism inherent in some nuclear isotopes; of these the proton, or hydrogen atom, is of particular interest for clinical applications. The magnetism in each nucleus is often referred to as spin. A strong, static magnetic field B0 is used to align spins, forming a magnetic density within the patient. A second, rotating magnetic field B1 (RF pulse) is applied for a short duration, which rotates the spins away from B0 in a process called excitation. After the spins are rotated away from B0, the RF pulse is turned off, and the spins precess about B0. As long as the spins are all pointing in the same direction at any one time (have phase coherence), they act in concert to create rapidly oscillating magnetic fields. These fields in turn create a current in an appropriately placed receiver coil, in a manner similar to that of an electrical generator. The precessing magnetization decays rapidly in a duration roughly given by the T2 time constant. At the same time, but at a slower rate, magnetization forms again along the direction of B0; the duration of this process is roughly expressed by the T1 time constant. The precessional frequency of each spin is proportional to the magnetic field experienced at the nucleus. Small variations in this magnetic field can have dramatic effects on the MR image, caused in part by loss of phase coherence. These magnetic field variations can arise because of magnet design, the magnetic properties (susceptibility) of tissues and other materials, and the nuclear environment unique to various sites within any given molecule. The loss of phase coherence can be effectively eliminated by the use of RF refocusing pulses. Conventional MR imaging experiments can be characterized as either gradient echo or spin echo, the latter indicating the use of a RF refocusing pulse, and by the parameters TR, TE, and flip angle alpha. Tissues, in turn, are characterized by their individual spin

  12. Spin Hall and Spin Nernst effect from first principles

    NASA Astrophysics Data System (ADS)

    Mertig, Ingrid

    2013-03-01

    Spintronics without magnetic materials is an interesting alternative to the existing spintronics applications. The spin Hall effect creates spin currents in nonmagnetic materials and avoids the problem of spin injection. Future applications of the spin Hall effect require two properties of the materials, a large spin Hall angle and a long spin diffusion length. Ab intio calculations based on density functional theory are a powerful tool to design the desired materials and to get insight into the underlying microscopic processes. We investigated the spin Hall effect in dilute alloys, in particular the intrinsic effect based on the Berry curvature as well as side-jump and the skew-scattering contributions. The results demonstrate that a large extrinsic spin Hall effect is determined by the differences between host and impurity concerning the spin-orbit interaction. It can be caused by light p scatterers as C and N in Au. A comparable large effect is observed for heavy p scatterers as Bi in Cu. An alternative way is to deposit impurities in the adatom position. Furthermore, we predict a spin current perpendicular to a temperature gradient. The phenomenon is called spin Nernst effect. The predicted spin currents can be comparably large as in the case of the spin Hall effect.

  13. Spin pumping by magnetopolaritons

    NASA Astrophysics Data System (ADS)

    Cao, Yunshan; Yan, Peng; Huebl, Hans; Goennenwein, Sebastian; Bauer, Gerrit

    2015-03-01

    Recent experiments report the strong coupling of microwaves to the magnetic insulator yttrium iron garnet with weakly damped magnetization dynamics. We developed a scattering approach to study the coupled magnetization and microwave cavities beyond the paramagnetic/macrospin and rotating wave approximations that are implicit in the Tavis-Cummings model. To this end we solve the coupled Landau-Lifshitz-Gilbert and Maxwell's equations for a thin film magnet in a microwave cavity, leading to rich ferromagnetic spin wave resonance spectra of the transmitted or absorbed microwaves. Our method is valid for the full parameter range spanning the weak to strong coupling limits. We demonstrate strong coupling achievement not only for the FMR mode but also for standing spin waves, although the lowest excitation has a decisive leading role for coupling strength. Spin pumping in FI|N bilayers as detected by inverse spin Hall voltages provides additional access to study strong coupling electrically. Funding from the European Union Seventh Framework Programme [FP7-People-2012-ITN] under Grant Agreement 316657 (SpinIcur).

  14. Spin hydrodynamic generation

    NASA Astrophysics Data System (ADS)

    Takahashi, R.; Matsuo, M.; Ono, M.; Harii, K.; Chudo, H.; Okayasu, S.; Ieda, J.; Takahashi, S.; Maekawa, S.; Saitoh, E.

    2016-01-01

    Magnetohydrodynamic generation is the conversion of fluid kinetic energy into electricity. Such conversion, which has been applied to various types of electric power generation, is driven by the Lorentz force acting on charged particles and thus a magnetic field is necessary. On the other hand, recent studies of spintronics have revealed the similarity between the function of a magnetic field and that of spin-orbit interactions in condensed matter. This suggests the existence of an undiscovered route to realize the conversion of fluid dynamics into electricity without using magnetic fields. Here we show electric voltage generation from fluid dynamics free from magnetic fields; we excited liquid-metal flows in a narrow channel and observed longitudinal voltage generation in the liquid. This voltage has nothing to do with electrification or thermoelectric effects, but turned out to follow a universal scaling rule based on a spin-mediated scenario. The result shows that the observed voltage is caused by spin-current generation from a fluid motion: spin hydrodynamic generation. The observed phenomenon allows us to make mechanical spin-current and electric generators, opening a door to fluid spintronics.

  15. Geometrically representing spin correlations

    NASA Astrophysics Data System (ADS)

    White, Ian G.; Mirasola, Anthony; Hollingsworth, Jacob; Mukherjee, Rick; Hazzard, Kaden R. A.

    2016-05-01

    We develop a general method to visualize spin correlations, and we demonstrate its usefulness in ultracold matter from fermions in lattices to trapped ions and ultracold molecules. Correlations are of fundamental interest in many-body physics: they characterize phases in condensed matter and AMO, and are required for quantum sensing and computing. However, it is often difficult to understand even the simplest correlations - for example between two spin-1/2's - directly from the components Cab = - for { a , b } ∈ { x , y , z } . Not only are the nine independent Cab unwieldy, but considering the components also obscures the natural geometric structure. For example, simple spin rotations lead to complex transformations among the nine Cab. We provide a one-to-one map between the spin correlations and certain three-dimensional objects, analogous to the map between single spins and Bloch vectors. This object makes the geometric structure of the correlations manifest. Moreover, much as one can reason geometrically about dynamics using a Bloch vector - e.g. a magnetic field causes it to precess and dephasing causes it to shrink - we show that analogous reasoning holds for our visualization method.

  16. Harnessing spin precession with dissipation

    PubMed Central

    Crisan, A. D.; Datta, S.; Viennot, J. J.; Delbecq, M. R.; Cottet, A.; Kontos, T.

    2016-01-01

    Non-collinear spin transport is at the heart of spin or magnetization control in spintronics devices. The use of nanoscale conductors exhibiting quantum effects in transport could provide new paths for that purpose. Here we study non-collinear spin transport in a quantum dot. We use a device made out of a single-wall carbon nanotube connected to orthogonal ferromagnetic electrodes. In the spin transport signals, we observe signatures of out of equilibrium spin precession that are electrically tunable through dissipation. This could provide a new path to harness spin precession in nanoscale conductors. PMID:26816050

  17. Harnessing spin precession with dissipation

    NASA Astrophysics Data System (ADS)

    Crisan, A. D.; Datta, S.; Viennot, J. J.; Delbecq, M. R.; Cottet, A.; Kontos, T.

    2016-01-01

    Non-collinear spin transport is at the heart of spin or magnetization control in spintronics devices. The use of nanoscale conductors exhibiting quantum effects in transport could provide new paths for that purpose. Here we study non-collinear spin transport in a quantum dot. We use a device made out of a single-wall carbon nanotube connected to orthogonal ferromagnetic electrodes. In the spin transport signals, we observe signatures of out of equilibrium spin precession that are electrically tunable through dissipation. This could provide a new path to harness spin precession in nanoscale conductors.

  18. Spin rectification induced by spin Hall magnetoresistance at room temperature

    NASA Astrophysics Data System (ADS)

    Wang, P.; Jiang, S. W.; Luan, Z. Z.; Zhou, L. F.; Ding, H. F.; Zhou, Y.; Tao, X. D.; Wu, D.

    2016-09-01

    We have experimentally and theoretically investigated the dc voltage generation in the heterostructure of Pt and yttrium iron garnet under the ferromagnetic resonance. Besides a symmetric Lorenz line shape dc voltage, an antisymmetric Lorenz line shape dc voltage is observed in field scan, which can solely originate from the spin rectification effect due to the spin Hall magnetoresistance. The angular dependence of the dc voltage is theoretically analyzed by taking into account both the spin pumping and the spin rectification effects. We find that the experimental results are in excellent agreement with the theoretical model, further identifying the spin Hall magnetoresistance origin of the spin rectification effect. Moreover, the spin pumping and the spin rectification effects are quantitatively separated by their different angular dependence at particular experimental geometry.

  19. Quantum spin transistor with a Heisenberg spin chain

    NASA Astrophysics Data System (ADS)

    Marchukov, O. V.; Volosniev, A. G.; Valiente, M.; Petrosyan, D.; Zinner, N. T.

    2016-10-01

    Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a control spin excitation in the central gate part of the spin chain results in either perfect transfer of an arbitrary state of a target spin between the weakly coupled input and output ports, or its complete blockade at the input port. We also discuss a possible proof-of-concept realization of the corresponding spin chain with a one-dimensional ensemble of cold atoms with strong contact interactions. Our scheme is generally applicable to various implementations of tunable spin chains, and it paves the way for the realization of integrated quantum logic elements.

  20. Quantum spin transistor with a Heisenberg spin chain

    PubMed Central

    Marchukov, O. V.; Volosniev, A. G.; Valiente, M.; Petrosyan, D.; Zinner, N. T.

    2016-01-01

    Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a control spin excitation in the central gate part of the spin chain results in either perfect transfer of an arbitrary state of a target spin between the weakly coupled input and output ports, or its complete blockade at the input port. We also discuss a possible proof-of-concept realization of the corresponding spin chain with a one-dimensional ensemble of cold atoms with strong contact interactions. Our scheme is generally applicable to various implementations of tunable spin chains, and it paves the way for the realization of integrated quantum logic elements. PMID:27721438

  1. Spin-orbit coupling and spin relaxation in phosphorene

    NASA Astrophysics Data System (ADS)

    Kurpas, Marcin; Gmitra, Martin; Fabian, Jaroslav

    We employ first principles density functional theory calculations to study intrinsic and extrinsic spin-orbit coupling in monolayer phosphorene. We also extract the spin-mixing amplitudes of the Bloch wave functions to give realistic estimates of the Elliott-Yafet spin relaxation rate. The most remarkable result is the striking anisotropy in both spin-orbit coupling and spin relaxation rates, which could be tested experimentally in spin injection experiments. We also identify spin hot spots in the electronic structure of phosphorene at accidental bands anticrossings. We compare the Elliott-Yafet with Dyakonov-Perel spin relaxation times, obtained from extrinsic couplings in an applied electric field. We also compare the results in phosphorene with those of black phosphorous. This work is supported by the DFG SPP 1538, SFB 689, and by the EU Seventh Framework Programme under Grant Agreement No. 604391 Graphene Flagship.

  2. Spin-Orbit Twisted Spin Waves: Group Velocity Control

    NASA Astrophysics Data System (ADS)

    Perez, F.; Baboux, F.; Ullrich, C. A.; D'Amico, I.; Vignale, G.; Karczewski, G.; Wojtowicz, T.

    2016-09-01

    We present a theoretical and experimental study of the interplay between spin-orbit coupling (SOC), Coulomb interaction, and motion of conduction electrons in a magnetized two-dimensional electron gas. Via a transformation of the many-body Hamiltonian we introduce the concept of spin-orbit twisted spin waves, whose energy dispersions and damping rates are obtained by a simple wave-vector shift of the spin waves without SOC. These theoretical predictions are validated by Raman scattering measurements. With optical gating of the density, we vary the strength of the SOC to alter the group velocity of the spin wave. The findings presented here differ from that of spin systems subject to the Dzyaloshinskii-Moriya interaction. Our results pave the way for novel applications in spin-wave routing devices and for the realization of lenses for spin waves.

  3. Spin filter and spin valve in ferromagnetic graphene

    NASA Astrophysics Data System (ADS)

    Song, Yu; Dai, Gang

    2015-06-01

    We propose and demonstrate that a EuO-induced and top-gated graphene ferromagnetic junction can be simultaneously operated as a spin filter and a spin valve. We attribute such a remarkable result to a coexistence of a half-metal band and a common energy gap for opposite spins in ferromagnetic graphene. We show that both the spin filter and the spin valve can be effectively controlled by a back gate voltage, and they survive for practical metal contacts and finite temperature. Specifically, larger single spin currents and on-state currents can be reached with contacts with work functions similar to graphene, and the spin filter can operate at higher temperature than the spin valve.

  4. Spinning fluids reactor

    DOEpatents

    Miller, Jan D; Hupka, Jan; Aranowski, Robert

    2012-11-20

    A spinning fluids reactor, includes a reactor body (24) having a circular cross-section and a fluid contactor screen (26) within the reactor body (24). The fluid contactor screen (26) having a plurality of apertures and a circular cross-section concentric with the reactor body (24) for a length thus forming an inner volume (28) bound by the fluid contactor screen (26) and an outer volume (30) bound by the reactor body (24) and the fluid contactor screen (26). A primary inlet (20) can be operatively connected to the reactor body (24) and can be configured to produce flow-through first spinning flow of a first fluid within the inner volume (28). A secondary inlet (22) can similarly be operatively connected to the reactor body (24) and can be configured to produce a second flow of a second fluid within the outer volume (30) which is optionally spinning.

  5. Spinning electroweak sphalerons

    SciTech Connect

    Radu, Eugen; Volkov, Mikhail S.

    2009-03-15

    We present numerical evidence for the existence of stationary spinning generalizations for the static sphaleron in the Weinberg-Salam theory. Our results suggest that, for any value of the mixing angle {theta}{sub W} and for any Higgs mass, the spinning sphalerons comprise a family labeled by their angular momentum J. For {theta}{sub W}{ne}0 they possess an electric charge Q=eJ, where e is the electron charge. Inside they contain a monopole-antimonopole pair and a spinning loop of electric current, and for large J, a Regge-type behavior. It is likely that these sphalerons mediate the topological transitions in sectors with J{ne}0, thus enlarging the number of transition channels. Their action decreases with J, which may considerably affect the total transition rate.

  6. Intrasplenic Arterial Aneurysms during Pregnancy

    PubMed Central

    Abu-khalaf, Mahmoud M. S.; Al-Ameer, Sokiyna M.; Smadi, Moath M.; Qatawneh, Ayman; Smara, Osama A.; Hadidy, Azmy T.

    2015-01-01

    Splenic artery aneurysms account for about 60% of all visceral aneurysms. Pregnancy is a risk factor for splenic artery aneurysms rupture with high maternal mortality and fetal loss. Intrasplenic arterial aneurysms are extremely rare and have not been reported to be associated with pregnancy. This report presents a 34-year-old woman during the second trimester, admitted with severe left upper quadrant and left shoulder pain. She had two uncomplicated intrasplenic aneurysms. Splenectomy was done. She delivered a full term healthy girl. This is the first report of acute abdomen during pregnancy caused by intrasplenic artery aneurysms with maternal and fetal survival. PMID:25810934

  7. Arterial pulse wave pressure transducer

    NASA Technical Reports Server (NTRS)

    Kim, C.; Gorelick, D.; Chen, W. (Inventor)

    1974-01-01

    An arterial pulse wave pressure transducer is introduced. The transducer is comprised of a fluid filled cavity having a flexible membrane disposed over the cavity and adapted to be placed on the skin over an artery. An arterial pulse wave creates pressure pulses in the fluid which are transduced, by a pressure sensitive transistor in direct contact with the fluid, into an electric signal. The electrical signal is representative of the pulse waves and can be recorded so as to monitor changes in the elasticity of the arterial walls.

  8. Zero-bias spin separation

    NASA Astrophysics Data System (ADS)

    Ganichev, Sergey D.; Bel'Kov, Vasily V.; Tarasenko, Sergey A.; Danilov, Sergey N.; Giglberger, Stephan; Hoffmann, Christoph; Ivchenko, Eougenious L.; Weiss, Dieter; Wegscheider, Werner; Gerl, Christian; Schuh, Dieter; Stahl, Joachim; de Boeck, Jo; Borghs, Gustaaf; Prettl, Wilhelm

    2006-09-01

    The generation, manipulation and detection of spin-polarized electrons in low-dimensional semiconductors are at the heart of spintronics. Pure spin currents, that is, fluxes of magnetization without charge current, are quite attractive in this respect. A paradigmatic example is the spin Hall effect, where an electrical current drives a transverse spin current and causes a non-equilibrium spin accumulation observed near the sample boundary. Here we provide evidence for an another effect causing spin currents which is fundamentally different from the spin Hall effect. In contrast to the spin Hall effect, it does not require an electric current to flow: without bias the spin separation is achieved by spin-dependent scattering of electrons in media with suitable symmetry. We show, by free-carrier absorption of terahertz (THz) radiation, that spin currents flow in a wide range of temperatures. Moreover, the experimental results provide evidence that simple electron gas heating by any means is already sufficient to yield spin separation due to spin-dependent energy-relaxation processes.

  9. Squeezed spin states: Squeezing the spin uncertainty relations

    NASA Technical Reports Server (NTRS)

    Kitagawa, Masahiro; Ueda, Masahito

    1993-01-01

    The notion of squeezing in spin systems is clarified, and the principle for spin squeezing is shown. Two twisting schemes are proposed as building blocks for spin squeezing and are shown to reduce the standard quantum noise, s/2, of the coherent S-spin state down to the order of S(sup 1/3) and 1/2. Applications to partition noise suppression are briefly discussed.

  10. Spin Echo in Synchrotrons

    SciTech Connect

    Chao, Alexander W.; Courant, Ernest D.; /Brookhaven

    2006-12-01

    As a polarized beam is accelerated through a depolarization resonance, its polarization is reduced by a well-defined calculable reduction factor. When the beam subsequently crosses a second resonance, the final beam polarization is considered to be reduced by the product of the two reduction factors corresponding to the two crossings, each calculated independently of the other. This is a good approximation when the spread of spin precession frequency {Delta}{nu}{sub spin} of the beam (particularly due to its energy spread) is sufficiently large that the spin precession phases of individual particles smear out completely during the time {tau} between the two crossings. This approximate picture, however, ignores two spin dynamics effects: an interference effect and a spin echo effect. This paper is to address these two effects. The interference effect occurs when {Delta}{nu}{sub spin} is too small, or when {tau} is too short, to complete the smearing process. In this case, the two resonance crossings interfere with each other, and the final polarization exhibits constructive or destructive patterns depending on the exact value of {tau}. Typically, the beam's energy spread is large and this interference effect does not occur. To study this effect, therefore, it is necessary to reduce the beam energy spread and to consider two resonance crossings very close to each other. The other mechanism, also due to the interplay between two resonance crossings, is spin echo. It turns out that even when the precession phases appear to be completely smeared between the two crossings, there will still be a sudden and short-lived echo signal of beam polarization at a time {tau} after the second crossing; the magnitude of which can be as large as 57%. This echo signal exists even when the beam has a sizable energy spread and when {tau} is very large, and could be a sensitive (albeit challenging) way to experimentally test the intricate spin dynamics in a synchrotron. After giving an

  11. Measuring Black Hole Spin

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    1999-09-01

    WE PROPOSE TO CARRY OUT A SYSTEMATIC STUDY OF EMISSION AND ABSORPTION SPECTRAL FEATURES THAT ARE OFTEN SEEN IN X-RAY SPECTRA OF BLACK HOLE BINARIES. THE EXCELLENT SENSITIVITY AND ENERGY RESOLUTION OF THE ACIS/HETG COMBINATION WILL NOT ONLY HELP RESOLVE AMBIGUITIES IN INTERPRETING THESE FEATURES, BUT MAY ALLOW MODELLING OF THE EMISSION LINE PROFILES IN DETAIL. THE PROFILES MAY CONTAIN INFORMATION ON SUCH FUNDAMENTAL PROPERTIES AS THE SPIN OF BLACK HOLES. THEREFORE, THIS STUDY COULD LEAD TO A MEASUREMENT OF BLACK HOLE SPIN FOR SELECTED SOURCES. THE RESULT CAN THEN BE DIRECTLY COMPARED WITH THOSE FROM PREVIOUS STUDIES BASED ON INDEPENDENT METHODS.

  12. Spin Wave Genie

    SciTech Connect

    2015-02-16

    The four-dimensional scattering function S(Q,w) obtained by inelastic neutron scattering measurements provides unique "dynamical fingerprints" of the spin state and interactions present in complex magnetic materials. Extracting this information however is currently a slow and complex process that may take an expert -depending on the complexity of the system- up to several weeks of painstaking work to complete. Spin Wave Genie was created to abstract and automate this process. It strives to both reduce the time to complete this analysis and make these calculations more accessible to a broader group of scientists and engineers.

  13. Spin Wave Genie

    2015-02-16

    The four-dimensional scattering function S(Q,w) obtained by inelastic neutron scattering measurements provides unique "dynamical fingerprints" of the spin state and interactions present in complex magnetic materials. Extracting this information however is currently a slow and complex process that may take an expert -depending on the complexity of the system- up to several weeks of painstaking work to complete. Spin Wave Genie was created to abstract and automate this process. It strives to both reduce themore » time to complete this analysis and make these calculations more accessible to a broader group of scientists and engineers.« less

  14. The mechanical and microscopic aspects of the deformation and fracture of a poly (ether urethane-urea) spun arterial prosthesis.

    PubMed

    Williams, D F; Zhong, S P; Doherty, P J

    1991-01-01

    The mechanical properties of a microporous, electrostatically spun poly (ether urethane-urea), used in the construction of arterial prostheses, have been examined, with particular reference to anisotropic, crack initiation processes and preconditioning. The results demonstrate considerable anisotropy in relation to samples derived from circumferential and longitudinal directions of the tube wall structure related to the spinning process. There is also a considerable difference in crack initiation on inner and outer surface of the arterial wall, again related to the processing conditions. The results provide an important contribution to an understanding of structure-property relationships in microporous arterial prosthesis.

  15. Artery of Percheron Infarction

    PubMed Central

    Vinod, K.V.; Kaaviya, R.; Arpita, Bhaumik

    2016-01-01

    Artery of Percheron (AOP) occlusion is a rare cause of ischemic stroke characterized by bilateral paramedian thalamic infarcts, with or without mesencephalic infarction. Clinically it presents with mental state disturbances, hypersomnolence, aphasia/dysarthria, amnesia and ocular movement disorders, including vertical gaze palsy. Here, we report a case of cardioembolic AOP infarction in a 37-year-old woman with rheumatic mitral valvular stenosis. This case is being reported to highlight the interesting clinical and neuroimaging features of this rare condition, and the differential diagnosis of AOP infarction on imaging have been discussed. PMID:27647964

  16. Artery of Percheron Infarction

    PubMed Central

    Vinod, K.V.; Kaaviya, R.; Arpita, Bhaumik

    2016-01-01

    Artery of Percheron (AOP) occlusion is a rare cause of ischemic stroke characterized by bilateral paramedian thalamic infarcts, with or without mesencephalic infarction. Clinically it presents with mental state disturbances, hypersomnolence, aphasia/dysarthria, amnesia and ocular movement disorders, including vertical gaze palsy. Here, we report a case of cardioembolic AOP infarction in a 37-year-old woman with rheumatic mitral valvular stenosis. This case is being reported to highlight the interesting clinical and neuroimaging features of this rare condition, and the differential diagnosis of AOP infarction on imaging have been discussed.

  17. Artery of Percheron Infarction.

    PubMed

    Vinod, K V; Kaaviya, R; Arpita, Bhaumik

    2016-07-01

    Artery of Percheron (AOP) occlusion is a rare cause of ischemic stroke characterized by bilateral paramedian thalamic infarcts, with or without mesencephalic infarction. Clinically it presents with mental state disturbances, hypersomnolence, aphasia/dysarthria, amnesia and ocular movement disorders, including vertical gaze palsy. Here, we report a case of cardioembolic AOP infarction in a 37-year-old woman with rheumatic mitral valvular stenosis. This case is being reported to highlight the interesting clinical and neuroimaging features of this rare condition, and the differential diagnosis of AOP infarction on imaging have been discussed. PMID:27647964

  18. Spin current swapping and spin hall effect in disordered metals

    NASA Astrophysics Data System (ADS)

    Saidaoui, Hamed; Pauyac, Christian; Manchon, Aurelien

    2015-03-01

    The conversion of charge currents into spin currents via the spin Hall effect has attracted intense experimental and theoretical efforts lately, providing an efficient means to generate electric signals and manipulate the magnetization of single layers. More recently, it was proposed that spin-dependent scattering induced by spin-orbit coupled impurities also produces a so-called spin swapping, i.e. an exchange between the spin angular momentum and linear momentum of itinerant electrons. In this work, we investigate the nature of spin swapping and its interplay with extrinsic spin Hall effect and spin relaxation in finite size normal metals. We use two complementary methods based on non-equilibrium Green's function technique. The first method consists in rigorously deriving the drift-diffusion equation of the spin accumulation in the presence of spin-orbit coupled impurities from quantum kinetics using Wigner expansion. The second method is the real-space tight binding modeling of a finite system in the presence of spin-orbit coupled disorder.

  19. Spin guides and spin splitters: waveguide analogies in one-dimensional spin chains.

    PubMed

    Makin, Melissa I; Cole, Jared H; Hill, Charles D; Greentree, Andrew D

    2012-01-01

    Here we show a mapping between waveguide theory and spin-chain transport, opening an alternative approach to solid-state quantum information transport. By applying temporally varying control profiles to a spin chain, we design a virtual waveguide or "spin guide" to conduct spin excitations along defined space-time trajectories of the chain. We show that the concepts of confinement, adiabatic bend loss, and beam splitting can be mapped from optical waveguide theory to spin guides, and hence to "spin splitters." Importantly, the spatial scale of applied control pulses is required to be large compared to the interspin spacing, thereby allowing the design of scalable control architectures.

  20. Retrograde superior mesenteric artery stenting for acute mesenteric arterial thrombosis.

    PubMed

    Do, Natalie; Wisniewski, Paul; Sarmiento, Jose; Vo, Trung; Aka, Paul K; Hsu, Jeffrey H; Tayyarah, Majid

    2010-08-01

    Retrograde superior mesenteric artery stenting (ROMS) represents a significant development in the treatment of acute mesenteric ischemia. Compared to traditional surgical mesenteric bypass, ROMS is a less invasive technique that avoids many complications associated with emergent mesenteric bypass. This case report illustrates that retrograde superior mesenteric artery (SMA) stenting is an option for the treatment of acute mesenteric ischemia for patients in extremis.

  1. Polariton condensates: Electrical spin switching

    NASA Astrophysics Data System (ADS)

    Liew, T. C. H.

    2016-10-01

    Ultra-low-power electronic switching of stable exciton-polariton spin states has now been achieved in a semiconductor microcavity. This opens a new route to the integration of spin-based photonics and electronics.

  2. True arterial system compliance estimated from apparent arterial compliance.

    PubMed

    Quick, C M; Berger, D S; Hettrick, D A; Noordergraaf, A

    2000-03-01

    A new method has been developed to estimate total arterial compliance from measured input pressure and flow. In contrast to other methods, this method does not rely on fitting the elements of a lumped model to measured data. Instead, it relies on measured input impedance and peripheral resistance to calculate the relationship of arterial blood volume to input pressure. Generally, this transfer function is a complex function of frequency and is called the apparent arterial compliance. At very low frequencies, the confounding effect of pulse wave reflection disappears, and apparent compliance becomes total arterial compliance. This study reveals that frequency components of pressure and flow below heart rate are generally necessary to obtain a valid estimate of compliance. Thus, the ubiquitous practice of estimating total arterial compliance from a single cardiac cycle is suspect under most circumstances, since a single cardiac cycle does not contain these frequencies. PMID:10784093

  3. The inferior epigastric artery arising from the internal iliac artery via a common trunk with the obturator artery.

    PubMed

    Won, Hyung-Sun; Won, Hyung-Jin; Oh, Chang-Seok; Han, Seung-Ho; Chung, In-Hyuk; Kim, Dong-Hoan

    2012-12-01

    We report a rare case of a left inferior epigastric artery arising from the internal iliac artery via a common trunk with the obturator artery in an 84-year-old female cadaver. A common trunk for the inferior epigastric and obturator arteries firstly originated from the left internal iliac artery, at 3.0 mm below the bifurcation of the left common iliac artery. This trunk ran straight between the left external iliac artery and left external iliac vein, and was finally divided into the left inferior epigastric and left obturator arteries just superior to the inguinal ligament. PMID:23301197

  4. Stochastic Evolution of Halo Spin

    NASA Astrophysics Data System (ADS)

    Kim, Juhan

    2015-08-01

    We will introduce an excursion set model for the evolution of halo spin from cosmological N-body simulations. A stochastic differential equation is derived from the definition of halo spin and the distribution of angular momentum changes are measured from simulations. The log-normal distribution of halo spin is found to be a natural consequence of the stochastic differential equation and the resulting spin distribution is found be a function of local environments, halo mass, and redshift.

  5. Nucleon spin structure

    NASA Astrophysics Data System (ADS)

    Zhu, Wei; Ruan, Jianhong

    2015-10-01

    This paper contains three parts relating to the nucleon spin structure in a simple picture of the nucleon: (i) The polarized gluon distribution in the proton is dynamically predicted starting from a low scale by using a nonlinear quantum chromodynamics (QCD) evolution equation — the Dokshitzer-Gribov-Lipatov-Altarelli-Paris (DGLAP) equation with the parton recombination corrections, where the nucleon is almost consisted only of valence quarks. We find that the contribution of the gluon polarization to the nucleon spin structure is much larger than the predictions of most other theories. This result suggests that a significant orbital angular momentum of the gluons is required to balance the gluon spin momentum. (ii) The spin structure function g1p of the proton is studied, where the perturbative evolution of parton distributions and nonperturbative vector meson dominance (VMD) model are used. We predict g1p asymptotic behavior at small x from lower Q2 to higher Q2. The results are compatible with the data including the early HERA estimations and COMPASS new results. (iii) The generalized Gerasimov-Drell-Hearn (GDH) sum rule is understood based on the polarized parton distributions of the proton with the higher twist contributions. A simple parameterized formula is proposed to clearly present the contributions of different components in the proton to Γ 1p(Q2). The results suggest a possible extended objects with size 0.2-0.3 fm inside the proton.

  6. Artificial frustrated spin systems

    NASA Astrophysics Data System (ADS)

    Perrin, Y.; Chioar, I. A.; Nguyen, V. D.; Lacour, D.; Hehn, M.; Montaigne, F.; Canals, B.; Rougemaille, N.

    2015-09-01

    Complex architectures of nanostructures are routinely elaborated using bottom-up or nanofabrication processes. This technological capability allows scientists to engineer materials with properties that do not exist in nature, but also to manufacture model systems to explore fundamental issues in condensed matter physics. Two-dimensional frustrated arrays of magnetic nanostructures are one class of systems for which theoretical predictions can be tested experimentally. These systems have been the subject of intense research in the last few years and allowed the investigation of a rich physics and fascinating phenomena, such as the exploration of the extensively degenerate ground-state manifolds of spin ice systems, the evidence of new magnetic phases in purely two-dimensional lattices, and the observation of pseudoexcitations involving classical analogues of magnetic monopoles. We show here, experimentally and theoretically, that simple magnetic geometries can lead to unconventional, non-collinear spin textures. For example, kagome arrays of inplane magnetized nano-islands do not show magnetic order. Instead, these systems are characterized by spin textures with intriguing properties, such as chirality, coexistence of magnetic order and disorder, and charge crystallization. Magnetic frustration effects in lithographically patterned kagome arrays of nanomagnets with out-of-plane magnetization also lead to an unusal, and still unknown, magnetic ground state manifold. Besides the influence of the lattice geometry, the micromagnetic nature of the elements constituting the arrays introduce the concept of chiral magnetic monopoles, bringing additional complexity into the physics of artificial frustrated spin systems.

  7. Stabilizing a spinning Skylab.

    NASA Technical Reports Server (NTRS)

    Seltzer, S. M.; Justice, D. W.; Schweitzer, G.; Patel, J. S.

    1972-01-01

    This paper presents the results of a study of the dynamics of a spinning Skylab space station. The stability of motion of several simplified models with flexible appendages was investigated. A digital simulation model that more accurately portrays the complex Skylab vehicle is described, and simulation results are compared with analytically derived results.

  8. Stabilizing a spinning Skylab

    NASA Technical Reports Server (NTRS)

    Seltzer, S. M.; Patel, J. S.; Justice, D. W.; Schweitzer, G. E.

    1972-01-01

    The results are presented of a study of the dynamics of a spinning Skylab space station. The stability of motion of several simplified models with flexible appendages was investigated. A digital simulation model that more accurately portrays the complex Skylab vehicle is described, and simulation results are compared with analytically derived results.

  9. Layered kagome spin ice

    NASA Astrophysics Data System (ADS)

    Hamp, James; Dutton, Sian; Mourigal, Martin; Mukherjee, Paromita; Paddison, Joseph; Ong, Harapan; Castelnovo, Claudio

    Spin ice materials provide a rare instance of emergent gauge symmetry and fractionalisation in three dimensions: the effective degrees of freedom of the system are emergent magnetic monopoles, and the extensively many `ice rule' ground states are those devoid of monopole excitations. Two-dimensional (kagome) analogues of spin ice have also been shown to display a similarly rich behaviour. In kagome ice however the ground-state `ice rule' condition implies the presence everywhere of magnetic charges. As temperature is lowered, an Ising transition occurs to a charge-ordered state, which can be mapped to a dimer covering of the dual honeycomb lattice. A second transition, of Kosterlitz-Thouless or three-state Potts type, occurs to a spin-ordered state at yet lower temperatures, due to small residual energy differences between charge-ordered states. Inspired by recent experimental capabilities in growing spin ice samples with selective (layered) substitution of non-magnetic ions, in this work we investigate the fate of the two ordering transitions when individual kagome layers are brought together to form a three-dimensional pyrochlore structure coupled by long range dipolar interactions. We also consider the response to substitutional disorder and applied magnetic fields.

  10. Does the Moon Spin?

    ERIC Educational Resources Information Center

    Collins, Robert; Simpson, Frances

    2007-01-01

    In this article, the authors explore the question, "Does the Moon spin?", and show how the question is investigated. They emphasise the importance of the process by which people work out what they know, by "learning from the inside out." They stress that those involved in science education have to challenge current conceptions and ideas, making…

  11. Supramolecular spin valves

    NASA Astrophysics Data System (ADS)

    Urdampilleta, M.; Klyatskaya, S.; Cleuziou, J.-P.; Ruben, M.; Wernsdorfer, W.

    2011-07-01

    Magnetic molecules are potential building blocks for the design of spintronic devices. Moreover, molecular materials enable the combination of bottom-up processing techniques, for example with conventional top-down nanofabrication. The development of solid-state spintronic devices based on the giant magnetoresistance, tunnel magnetoresistance and spin-valve effects has revolutionized magnetic memory applications. Recently, a significant improvement of the spin-relaxation time has been observed in organic semiconductor tunnel junctions, single non-magnetic molecules coupled to magnetic electrodes have shown giant magnetoresistance and hybrid devices exploiting the quantum tunnelling properties of single-molecule magnets have been proposed. Herein, we present an original spin-valve device in which a non-magnetic molecular quantum dot, made of a single-walled carbon nanotube contacted with non-magnetic electrodes, is laterally coupled through supramolecular interactions to TbPc2 single-molecule magnets (Pc=phthalocyanine). Their localized magnetic moments lead to a magnetic field dependence of the electrical transport through the single-walled carbon nanotube, resulting in magnetoresistance ratios up to 300% at temperatures less than 1 K. We thus demonstrate the functionality of a supramolecular spin valve without magnetic leads. Our results open up prospects of new spintronic devices with quantum properties.

  12. Supramolecular spin valves.

    PubMed

    Urdampilleta, M; Klyatskaya, S; Cleuziou, J-P; Ruben, M; Wernsdorfer, W

    2011-07-01

    Magnetic molecules are potential building blocks for the design of spintronic devices. Moreover, molecular materials enable the combination of bottom-up processing techniques, for example with conventional top-down nanofabrication. The development of solid-state spintronic devices based on the giant magnetoresistance, tunnel magnetoresistance and spin-valve effects has revolutionized magnetic memory applications. Recently, a significant improvement of the spin-relaxation time has been observed in organic semiconductor tunnel junctions, single non-magnetic molecules coupled to magnetic electrodes have shown giant magnetoresistance and hybrid devices exploiting the quantum tunnelling properties of single-molecule magnets have been proposed. Herein, we present an original spin-valve device in which a non-magnetic molecular quantum dot, made of a single-walled carbon nanotube contacted with non-magnetic electrodes, is laterally coupled through supramolecular interactions to TbPc(2) single-molecule magnets (Pc=phthalocyanine). Their localized magnetic moments lead to a magnetic field dependence of the electrical transport through the single-walled carbon nanotube, resulting in magnetoresistance ratios up to 300% at temperatures less than 1 K. We thus demonstrate the functionality of a supramolecular spin valve without magnetic leads. Our results open up prospects of new spintronic devices with quantum properties. PMID:21685902

  13. Transverse Spin at RHIC

    NASA Astrophysics Data System (ADS)

    Wang, Xiaorong

    2016-03-01

    In recent years, there has been exciting development in both experimental and theoretical studies of transverse spin asymmetries in polarized p+p and and DIS collisions. As a unique polarized proton-proton collider, Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) provides a unique opportunity to investigate the novel physics mechanisms that cause the large single spin asymmetry at the forward rapidity. Both PHENIX and STAR experiments have been studying the transverse spin asymmetries with a variety of final state particles in different kinematic regimes since 2006. Especially, recent theoretical development on scattering a polarized probe on the saturated nuclear may provide a unique way to probe the gluon and quark TMDs. RHIC successfully ran polarized p+Au collisions in 2015. We will expect to have new results from polarized d+Au to compare with existing results from p+p collision to extend our understanding of QCD. Further more, In 2015, PHENIX installed MPC-ex calorimeter at very forward region to measure direct photon AN and STAR installed Roman Pots to study the diffractive events in polarized p+p and p+Au collisions. The recent results on transverse polarized p+p and p+Au collisions from both PHENIX and STAR experiments will be presented in this talk. I will also briefly discuss the possibility for the transverse Spin program at future experiments sPHENIX and forward sPHENIX at RHIC. Supported by US Department of Energy and RIKEN Brookhaven Research Center.

  14. An overview of spin physics

    SciTech Connect

    Prescott, C.Y.

    1991-07-01

    Spin physics is playing an increasingly important role in high energy experiments and theory. This review looks at selected topics in high energy spin physics that were discussed at the 9th International Symposium on High Energy Spin Physics at Bonn in September 1990.

  15. Spin Transport in Semiconductor heterostructures

    SciTech Connect

    Domnita Catalina Marinescu

    2011-02-22

    The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.

  16. Microwave generation by spin Hall nanooscillators with nanopatterned spin injector

    SciTech Connect

    Zholud, A. Urazhdin, S.

    2014-09-15

    We experimentally study spin Hall nano-oscillators based on Pt/ferromagnet bilayers with nanopatterned Pt spin injection layer. We demonstrate that both the spectral characteristics and the electrical current requirements can be simultaneously improved by reducing the spin injection area. Moreover, devices with nanopatterned Pt spin injector exhibit microwave generation over a wide temperature range that extends to room temperature. Studies of devices with additional Pt spacers under the device electrodes show that the oscillation characteristics are affected not only by the spin injection geometry but also by the effects of Pt/ferromagnet interface on the dynamical properties of the ferromagnet.

  17. Gluonic Spin Contribution to Proton Spin at NLO

    SciTech Connect

    Casey, Andrew

    2011-05-24

    In 1988, when the EMC results showed that the quarks had a much smaller contribution to the spin of the proton than previously thought, the 'Proton Spin Crisis' began. Since then, considerable effort has been directed into discovering the main contributors to proton spin and how much each contributes. One such contributor is the gluonic spin component. QCD NLO evolution equations are combined with boundary conditions obtained from heavy quark decoupling expressions to evolve the equations from infinity to the mass of the charm quark in order to determine the gluonic spin contribution.

  18. Computer measurement of arterial disease

    NASA Technical Reports Server (NTRS)

    Armstrong, J.; Selzer, R. H.; Barndt, R.; Blankenhorn, D. H.; Brooks, S.

    1980-01-01

    Image processing technique quantifies human atherosclerosis by computer analysis of arterial angiograms. X-ray film images are scanned and digitized, arterial shadow is tracked, and several quantitative measures of lumen irregularity are computed. In other tests, excellent agreement was found between computer evaluation of femoral angiograms on living subjects and evaluation by teams of trained angiographers.

  19. Epigenetics and Peripheral Artery Disease.

    PubMed

    Golledge, Jonathan; Biros, Erik; Bingley, John; Iyer, Vikram; Krishna, Smriti M

    2016-04-01

    The term epigenetics is usually used to describe inheritable changes in gene function which do not involve changes in the DNA sequence. These typically include non-coding RNAs, DNA methylation and histone modifications. Smoking and older age are recognised risk factors for peripheral artery diseases, such as occlusive lower limb artery disease and abdominal aortic aneurysm, and have been implicated in promoting epigenetic changes. This brief review describes studies that have associated epigenetic factors with peripheral artery diseases and investigations which have examined the effect of epigenetic modifications on the outcome of peripheral artery diseases in mouse models. Investigations have largely focused on microRNAs and have identified a number of circulating microRNAs associated with human peripheral artery diseases. Upregulating or antagonising a number of microRNAs has also been reported to limit aortic aneurysm development and hind limb ischemia in mouse models. The importance of DNA methylation and histone modifications in peripheral artery disease has been relatively little studied. Whether circulating microRNAs can be used to assist identification of patients with peripheral artery diseases and be modified in order to improve the outcome of peripheral artery disease will require further investigation.

  20. Development and Application of Spin Traps, Spin Probes, and Spin Labels.

    PubMed

    Bagryanskaya, Elena G; Krumkacheva, Olesya A; Fedin, Matvey V; Marque, Sylvain R A

    2015-01-01

    This chapter focuses on major achievements of the last decade in the synthesis and applications of spin traps, spin probes, and spin labels. Our discussion on spin trapping is mainly concerned with novel aspects of nitrones used as spin traps and with the kinetics caused by bioreductants. The second part of the chapter deals with recent developments in site-directed spin labeling (SDSL) for studying structure and functions of proteins and nucleic acids. We focus on SDSL EPR distance measurements using advanced trityl and nitroxide labels, on new approaches for incorporation of spin labels in biomolecules, and finally, on recent room/physiological temperature measurements made feasible by these novel spin labels. PMID:26478492

  1. Spin Circuit Representation of Spin Pumping in Topological Insulators

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal

    Earlier we developed spin circuit representation of spin pumping and combined it with the spin circuit representation for the inverse spin Hall effect to show that it reproduces the established results in literature. Here we construct the spin circuit representation of spin pumping in topological insulators. The discovery of spin-polarized surface states in three-dimensional (3D) topological insulators (TIs) with strong spin-orbit coupling is promising for the development of spintronics. There is considerable bulk conduction too in 3D TIs (e.g., Bi2Se3) apart from possessing the surface states. We utilize the spin circuit model for spin orbit torques in topological insulator surface states to develop the equivalent circuit model of spin pumping in topological insulators. Such equivalent circuit model developed here can be utilized to analyze available experimental results and evaluate more complex structures. This work was supported by FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA.

  2. Thermal creation of a spin current by Seebeck spin tunneling

    NASA Astrophysics Data System (ADS)

    Jansen, R.; Le Breton, J. C.; Deac, A. M.; Saito, H.; Yuasa, S.

    2013-09-01

    The thermoelectric analog of spin-polarized tunneling, namely Seebeck spin tunneling, is a recently discovered phenomenon that arises from the spin-dependent Seebeck coefficient of a magnetic tunnel contact. In a tunnel junction with one ferromagnetic electrode and one non-magnetic electrode, a temperature difference between the two electrodes creates a spin current across the contact. Here, the basic principle and the observation of Seebeck spin tunneling are described. It is shown how it can be used to create a spin accumulation in silicon driven by a heat flow across a magnetic tunnel contact, without a charge tunnel current. The sign of the spin current depends on the direction of the heat flow, whereas its magnitude is anisotropic, i.e., dependent on the absolute orientation of the magnetization of the ferromagnet. The connection between Seebeck spin tunneling and the tunnel magneto-Seebeck effect, observed in metal magnetic tunnel junctions, is also clarified. Seebeck spin tunneling may be used to convert waste heat into useful thermal spin currents that aid or replace electrical spin current, and thereby improve the energy efficiency of spintronic devices and technologies.

  3. Spin Hall Conductivity and Spin Chern Number for Dirac Systems

    NASA Astrophysics Data System (ADS)

    Yunt, Elif; Dayi, Omer Faruk

    A semiclassical differential form formalism of the spin Hall effect for Dirac systems is presented. In this formalism, space coordinates and momenta are usual dynamical variables, whereas spin is not a dynamical degree of freedom. Spin depicts itself in the matrix-valuedness of equations of motion. We demonstrate that the main contribution to the spin Hall conductivity is given by the spin Chern number whether the spin is conserved or not at the quantum level. We illustrated the formulation within the Kane-Mele model of graphene in the absence and in the presence of the Rashba spin-orbit coupling term. Kane-Mele Model of graphene, which incorporates intrinsic spin-orbit interaction, constitutes the first example of a two dimensional topological insulator. We established the anomalous Hall conductivity as well as the spin Hall conductivity from the term linear in the electric field and the Berry curvature in the the anamolous velocity term. In a basis where the component of spin under consideration is diagonal this term is diagonal. We argue that this semiclassical procedure of calculating the spin Hall conductivity can be generalized to any dimension.

  4. Spin-transfer torque induced spin waves in antiferromagnetic insulators

    NASA Astrophysics Data System (ADS)

    Daniels, Matthew; Guo, Wei; Stocks, G. Malcolm; Xiao, Di; Xiao, Jiang

    2015-03-01

    We explore the possibility of exciting spin waves in insulating antiferromagnetic films by injecting spin current at the surface. We analyze both magnetically compensated and uncompensated interfaces. We find that the spin current induced spin-transfer torque can excite spin waves in insulating antiferromagnetic materials and that the chirality of the excited spin wave is determined by the polarization of the injected spin current. Furthermore, the presence of magnetic surface anisotropy can greatly increase the accessibility of these excitations. Supported by NSF EFRI-1433496 (M.W.D), U.S. DOE Office of Basic Energy Sciences, Materials Sciences and Engineering (D.X. & G.M.S.), Major State Basic Research Project of China and National Natural Science Foundation of China (W.G. and J.X.).

  5. Excitation of coherent propagating spin waves by pure spin currents

    PubMed Central

    Demidov, Vladislav E.; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O.

    2016-01-01

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics. PMID:26818232

  6. State diagram of an orthogonal spin transfer spin valve device

    SciTech Connect

    Ye, Li; Wolf, Georg; Pinna, Daniele; Chaves-O'Flynn, Gabriel D.; Kent, Andrew D.

    2015-05-21

    We present the switching characteristics of a spin-transfer device that incorporates a perpendicularly magnetized spin-polarizing layer with an in-plane magnetized free and fixed magnetic layer, known as an orthogonal spin transfer spin valve device. This device shows clear switching between parallel (P) and antiparallel (AP) resistance states and the reverse transition (AP → P) for both current polarities. Further, hysteretic transitions are shown to occur into a state with a resistance intermediate between that of the P and AP states, again for both current polarities. These unusual spin-transfer switching characteristics can be explained within a simple macrospin model that incorporates thermal fluctuations and considers a spin-polarized current that is tilted with respect to the free layer's plane, due to the presence of the spin-transfer torque from the polarizing layer.

  7. Ultrafast Optical Spin Echo for Electron Spins in Semiconductors

    SciTech Connect

    Clark, Susan M.; Fu, Kai-Mei C.; Zhang Qiang; Ladd, Thaddeus D.; Yamamoto, Yoshihisa; Stanley, Colin

    2009-06-19

    Spin-based quantum computing and magnetic resonance techniques rely on the ability to measure the coherence time T{sub 2} of a spin system. We report on the experimental implementation of all-optical spin echo to determine the T{sub 2} time of a semiconductor electron-spin system. We use three ultrafast optical pulses to rotate spins an arbitrary angle and measure an echo signal as the time between pulses is lengthened. Unlike previous spin-echo techniques using microwaves, ultrafast optical pulses allow clean T{sub 2} measurements of systems with dephasing times (T{sub 2}*) fast in comparison to the time scale for microwave control. This demonstration provides a step toward ultrafast optical dynamic decoupling of spin-based qubits.

  8. Hydrodynamics of spin-polarized transport and spin pendulum

    SciTech Connect

    Gurzhi, R. N. Kalinenko, A. N.; Kopeliovich, A. I.; Pyshkin, P. V.; Yanovsky, A. V.

    2007-07-15

    The dynamics of a nonequilibrium spin system dominated by collisions preserving the total quasimomentum of the interacting electrons and quasiparticles is considered. An analysis of the derived hydrodynamic equations shows that weakly attenuated spin-polarization waves associated with an oscillating drift current can exist in a magnetically inhomogeneous conducting ring. Spin-polarized transport in a ballistic regime of wave propagation through a conductor is also considered, and a simple method is proposed for distinguishing these waves from spin and current oscillations that develop in the hydrodynamic regime. It is shown that a potential difference arises between the leads of an open nonuniformly spin-polarized conductor as a manifestation of spin polarization of electron density. This spin-mediated electrical phenomenon occurs in both hydrodynamic and diffusive limits.

  9. Spinning compact binary : Independent variables and dynamically preserved spin configurations

    SciTech Connect

    Gergely, Laszlo Arpad

    2010-04-15

    We establish the set of independent variables suitable to monitor the complicated evolution of the spinning compact binary during the inspiral. Our approach is valid up to the second post-Newtonian order, including leading order spin-orbit, spin-spin and mass quadrupole-mass monopole effects, for generic (noncircular, nonspherical) orbits. Then, we analyze the conservative spin dynamics in terms of these variables. We prove that the only binary black hole configuration allowing for spin precessions with equal angular velocities about a common instantaneous axis roughly aligned to the normal of the osculating orbit, is the equal mass and parallel (aligned or antialigned) spin configuration. This analytic result puts limitations on what particular configurations can be selected in numerical investigations of compact binary evolutions, even in those including only the last orbits of the inspiral.

  10. Pseudospin, real spin, and spin polarization of photoemitted electrons

    NASA Astrophysics Data System (ADS)

    Yu, Rui; Weng, Hongming; Fang, Zhong; Dai, Xi

    2016-08-01

    In this paper, we discuss the connections between pseudospin, real spin of electrons in a material, and spin polarization of photoemitted electrons out of a material. By investigating these three spin textures for Bi2Se3 and SmB6 compounds, we find that the spin orientation of photoelectrons for SmB6 has a different correspondence to pseudospin and real spin compared to Bi2Se3 , due to the different symmetry properties of the photoemission matrix between the initial and final states. We calculate the spin polarization and circular dichroism spectra of photoemitted electrons for both compounds, which can be detected by spin-resolved and circular dichroism angle-resolved photoemission spectroscopy experiments.

  11. Patent arterial duct.

    PubMed

    Forsey, Jonathan T; Elmasry, Ola A; Martin, Robin P

    2009-07-10

    Patent arterial duct (PAD) is a congenital heart abnormality defined as persistent patency in term infants older than three months. Isolated PAD is found in around 1 in 2000 full term infants. A higher prevalence is found in preterm infants, especially those with low birth weight. The female to male ratio is 2:1. Most patients are asymptomatic when the duct is small. With a moderate-to-large duct, a characteristic continuous heart murmur (loudest in the left upper chest or infraclavicular area) is typical. The precordium may be hyperactive and peripheral pulses are bounding with a wide pulse pressure. Tachycardia, exertional dyspnoea, laboured breathing, fatigue or poor growth are common. Large shunts may lead to failure to thrive, recurrent infection of the upper respiratory tract and congestive heart failure. In the majority of cases of PAD there is no identifiable cause. Persistence of the duct is associated with chromosomal aberrations, asphyxia at birth, birth at high altitude and congenital rubella. Occasional cases are associated with specific genetic defects (trisomy 21 and 18, and the Rubinstein-Taybi and CHARGE syndromes). Familial occurrence of PAD is uncommon and the usual mechanism of inheritance is considered to be polygenic with a recurrence risk of 3%. Rare families with isolated PAD have been described in which the mode of inheritance appears to be dominant or recessive. Familial incidence of PAD has also been linked to Char syndrome, familial thoracic aortic aneurysm/dissection associated with patent arterial duct, and familial patent arterial duct and bicuspid aortic valve associated with hand abnormalities. Diagnosis is based on clinical examination and confirmed with transthoracic echocardiography. Assessment of ductal blood flow can be made using colour flow mapping and pulsed wave Doppler. Antenatal diagnosis is not possible, as PAD is a normal structure during antenatal life. Conditions with signs and symptoms of pulmonary overcirculation

  12. Patent arterial duct

    PubMed Central

    Forsey, Jonathan T; Elmasry, Ola A; Martin, Robin P

    2009-01-01

    Patent arterial duct (PAD) is a congenital heart abnormality defined as persistent patency in term infants older than three months. Isolated PAD is found in around 1 in 2000 full term infants. A higher prevalence is found in preterm infants, especially those with low birth weight. The female to male ratio is 2:1. Most patients are asymptomatic when the duct is small. With a moderate-to-large duct, a characteristic continuous heart murmur (loudest in the left upper chest or infraclavicular area) is typical. The precordium may be hyperactive and peripheral pulses are bounding with a wide pulse pressure. Tachycardia, exertional dyspnoea, laboured breathing, fatigue or poor growth are common. Large shunts may lead to failure to thrive, recurrent infection of the upper respiratory tract and congestive heart failure. In the majority of cases of PAD there is no identifiable cause. Persistence of the duct is associated with chromosomal aberrations, asphyxia at birth, birth at high altitude and congenital rubella. Occasional cases are associated with specific genetic defects (trisomy 21 and 18, and the Rubinstein-Taybi and CHARGE syndromes). Familial occurrence of PAD is uncommon and the usual mechanism of inheritance is considered to be polygenic with a recurrence risk of 3%. Rare families with isolated PAD have been described in which the mode of inheritance appears to be dominant or recessive. Familial incidence of PAD has also been linked to Char syndrome, familial thoracic aortic aneurysm/dissection associated with patent arterial duct, and familial patent arterial duct and bicuspid aortic valve associated with hand abnormalities. Diagnosis is based on clinical examination and confirmed with transthoracic echocardiography. Assessment of ductal blood flow can be made using colour flow mapping and pulsed wave Doppler. Antenatal diagnosis is not possible, as PAD is a normal structure during antenatal life. Conditions with signs and symptoms of pulmonary overcirculation

  13. Spin Hall controlled magnonic microwaveguides

    SciTech Connect

    Demidov, V. E.; Urazhdin, S.; Rinkevich, A. B.; Reiss, G.; Demokritov, S. O.

    2014-04-14

    We use space-resolved magneto-optical spectroscopy to study the influence of spin Hall effect on the excitation and propagation of spin waves in microscopic magnonic waveguides. We find that the spin Hall effect not only increases the spin-wave propagation length, but also results in an increased excitation efficiency due to the increase of the dynamic susceptibility in the vicinity of the inductive antenna. We show that the efficiency of the propagation length enhancement is strongly dependant on the type of the excited spin-wave mode and its wavelength.

  14. RHIC spin flipper commissioning results

    SciTech Connect

    Bai M.; Roser, T.; Dawson, C.; Kewisch, J.; Makdisi, Y.; Oddo, P.; Pai, C.; Pile, P.

    2012-05-20

    The five AC dipole RHIC spin flipper design in the RHIC Blue ring was first tested during the RHIC 2012 polarized proton operation. The advantage of this design is to eliminate the vertical coherent betatron oscillations outside the spin flipper. The closure of each ac dipole vertical bump was measured with orbital response as well as spin. The effect of the rotating field on the spin motion by the spin flipper was also confirmed by measuring the suppressed resonance at Q{sub s} = 1 - Q{sub osc}.

  15. Spontaneous Coronary Artery Dissection.

    PubMed

    Tweet, Marysia S; Gulati, Rajiv; Hayes, Sharonne N

    2016-07-01

    Spontaneous coronary artery dissection is an important etiology of nonatherosclerotic acute coronary syndrome, myocardial infarction, and sudden death. Innovations in the catheterization laboratory including optical coherence tomography and intravascular ultrasound have enhanced the ability to visualize intimal disruption and intramural hematoma associated with SCAD. Formerly considered "rare," these technological advances and heightened awareness suggest that SCAD is more prevalent than prior estimates. SCAD is associated with female sex, young age, extreme emotional stress, or extreme exertion, pregnancy, and fibromuscular dysplasia. The clinical characteristics and management strategies of SCAD patients are different than for atherosclerotic heart disease and deserve specific consideration. This review will highlight recent discoveries about SCAD as well as describe current efforts to elucidate remaining gaps in knowledge.

  16. Spontaneous Coronary Artery Dissection.

    PubMed

    Tweet, Marysia S; Gulati, Rajiv; Hayes, Sharonne N

    2016-07-01

    Spontaneous coronary artery dissection is an important etiology of nonatherosclerotic acute coronary syndrome, myocardial infarction, and sudden death. Innovations in the catheterization laboratory including optical coherence tomography and intravascular ultrasound have enhanced the ability to visualize intimal disruption and intramural hematoma associated with SCAD. Formerly considered "rare," these technological advances and heightened awareness suggest that SCAD is more prevalent than prior estimates. SCAD is associated with female sex, young age, extreme emotional stress, or extreme exertion, pregnancy, and fibromuscular dysplasia. The clinical characteristics and management strategies of SCAD patients are different than for atherosclerotic heart disease and deserve specific consideration. This review will highlight recent discoveries about SCAD as well as describe current efforts to elucidate remaining gaps in knowledge. PMID:27216840

  17. Determination of the spin diffusion length in germanium by spin optical orientation and electrical spin injection

    NASA Astrophysics Data System (ADS)

    Rinaldi, C.; Bertoli, S.; Asa, M.; Baldrati, L.; Manzoni, C.; Marangoni, M.; Cerullo, G.; Bianchi, M.; Sordan, R.; Bertacco, R.; Cantoni, M.

    2016-10-01

    The measurement of the spin diffusion length and/or lifetime in semiconductors is a key issue for the realisation of spintronic devices, exploiting the spin degree of freedom of carriers for storing and manipulating information. In this paper, we address such parameters in germanium (0 0 1) at room temperature (RT) by three different measurement methods. Exploiting optical spin orientation in the semiconductor and spin filtering across an insulating MgO barrier, the dependence of the resistivity on the spin of photo-excited carriers in Fe/MgO/Ge spin photodiodes (spin-PDs) was electrically detected. A spin diffusion length of 0.9  ±  0.2 µm was obtained by fitting the photon energy dependence of the spin signal by a mathematical model. Electrical techniques, comprising non-local four-terminal and Hanle measurements performed on CoFeB/MgO/Ge lateral devices, led to spin diffusion lengths of 1.3  ±  0.2 µm and 1.3  ±  0.08 µm, respectively. Despite minor differences due to experimental details, the order of magnitude of the spin diffusion length is the same for the three techniques. Although standard electrical methods are the most employed in semiconductor spintronics for spin diffusion length measurements, here we demonstrate optical spin orientation as a viable alternative for the determination of the spin diffusion length in semiconductors allowing for optical spin orientation.

  18. Spin Funneling for Enhanced Spin Injection into Ferromagnets

    PubMed Central

    Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

    2016-01-01

    It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory. PMID:27374496

  19. Spin Funneling for Enhanced Spin Injection into Ferromagnets

    NASA Astrophysics Data System (ADS)

    Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

    2016-07-01

    It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory.

  20. All-electric spin transistor using perpendicular spins

    NASA Astrophysics Data System (ADS)

    Kim, Ji Hoon; Bae, Joohyung; Min, Byoung-Chul; Kim, Hyung-jun; Chang, Joonyeon; Koo, Hyun Cheol

    2016-04-01

    All-electric spin transistor is demonstrated using perpendicular spins in an InAs quantum well channel. For the injection and detection of perpendicular spins in the quantum well channel, we use Tb20Fe62Co18/Co40Fe40B20 electrodes, where the Tb20Fe62Co18 layer produces the perpendicular magnetization and the Co40Fe40B20 layer enhances the spin polarization. In this spin transistor device, a gate-controlled spin signal as large as 80 mΩ is observed at 10 K without an external magnetic field. In order to confirm the spin injection and relaxation independently, we measure the three-terminal Hanle effect with an in-plane magnetic field, and obtain a spin signal of 1.7 mΩ at 10 K. These results clearly present that the electric field is an efficient way to modulate spin orientation in a strong spin-orbit interaction system.

  1. Spin Funneling for Enhanced Spin Injection into Ferromagnets.

    PubMed

    Sayed, Shehrin; Diep, Vinh Q; Camsari, Kerem Yunus; Datta, Supriyo

    2016-01-01

    It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory. PMID:27374496

  2. Spin squeezing and entanglement for an arbitrary spin

    NASA Astrophysics Data System (ADS)

    Vitagliano, Giuseppe; Apellaniz, Iagoba; Egusquiza, Iñigo L.; Tóth, Géza

    2014-03-01

    A complete set of generalized spin-squeezing inequalities is derived for an ensemble of particles with an arbitrary spin. Our conditions are formulated with the first and second moments of the collective angular momentum coordinates. A method for mapping the spin-squeezing inequalities for spin-1/2 particles to entanglement conditions for spin-j particles is also presented. We apply our mapping to obtain a generalization of the original spin-squeezing inequality to higher spins. We show that, for large particle numbers, a spin-squeezing parameter for entanglement detection based on one of our inequalities is strictly stronger than the original spin-squeezing parameter defined in Sørensen et al. [Nature (London) 409, 63 (2001), 10.1038/35051038]. We present a coordinate system independent form of our inequalities that contains, besides the correlation and covariance tensors of the collective angular momentum operators, the nematic tensor appearing in the theory of spin nematics. Finally, we discuss how to measure the quantities appearing in our inequalities in experiments.

  3. Spin noise in the anisotropic central spin model

    NASA Astrophysics Data System (ADS)

    Hackmann, Johannes; Anders, Frithjof B.

    2014-01-01

    Spin-noise measurements can serve as a direct probe for the microscopic decoherence mechanism of an electronic spin in semiconductor quantum dots (QDs). We have calculated the spin-noise spectrum in the anisotropic central spin model using a Chebyshev expansion technique which exactly accounts for the dynamics up to an arbitrary long but fixed time in a finite-size system. In the isotropic case, describing QD charge with a single electron, the short-time dynamics is in good agreement with quasistatic approximations for the thermodynamic limit. The spin-noise spectrum, however, shows strong deviations at low frequencies with a power-law behavior of ω-3/4 corresponding to a t-1/4 decay at intermediate and long times. In the Ising limit, applicable to QDs with heavy-hole spins, the spin-noise spectrum exhibits a threshold behavior of (ω-ωL)-1/2 above the Larmor frequency ωL=gμBB. In the generic anisotropic central spin model we have found a crossover from a Gaussian type of spin-noise spectrum to a more Ising-type spectrum with increasing anisotropy in a finite magnetic field. In order to make contact with experiments, we present ensemble averaged spin-noise spectra for QD ensembles charged with single electrons or holes. The Gaussian-type noise spectrum evolves to a more Lorentzian shape spectrum with increasing spread of characteristic time scales and g factors of the individual QDs.

  4. Pure spin current transport in Alq3 by spin pumping

    NASA Astrophysics Data System (ADS)

    Jiang, Shengwei; Wang, Peng; Luan, Zhongzhi; Tao, Xinde; Ding, Haifeng; Wu, Di

    2015-03-01

    The use of organic semiconductors (OSCs) in spintronics has aroused considerable interests, owing to their much longer spin-relaxation times of OSCs than those of inorganic counterparts. The most studied example is the organic spin valve (OSV), in which magnetoresistance (MR) effect is frequently reported. However, studies on pure spin current injection and transport in OSCs are scarce. Recently, the pioneering work by Watanabe et al. demonstrated that pure spin current can be pumped into and propagates in semiconducting polymers. In the present work we extend the study to small molecule OSCs, and demonstrate that pure spin current can be injected into Alq3 from the adjacent magnetic insulator Y3Fe5O12 (YIG) by spin pumping. The pure spin current is detected by inverse spin Hall effect (ISHE) in Pd after propagation through Alq3. From the ISHE voltage VISHE as a function of the Alq3 thickness, the spin diffusion length is determined to be ~ 50 nm and does not depend on temperature. This result indicates the MR decrease as increasing temperature in OSVs is not due to the reduced spin diffusion length.

  5. Left Main Coronary Artery Aneurysm

    PubMed Central

    Doustkami, Hossein; Maleki, Nasrollah; Tavosi, Zahra

    2016-01-01

    Aneurysms of the left main coronary artery are exceedingly rare clinical entities, encountered incidentally in approximately 0.1% of patients who undergo routine angiography. The most common cause of coronary artery aneurysms is atherosclerosis. Angiography is the gold standard for diagnosis and treatment. Depending on the severity of the coexisting coronary stenosis, patients with left main coronary artery aneurysms can be effectively managed either surgically or pharmacologically. We herein report a case of left main coronary artery aneurysm in a 72-year-old man with a prior history of hypertension presenting to our hospital because of unstable angina. The electrocardiogram showed ST-segment depression and T-wave inversion in the precordial leads. All the data of blood chemistry were normal. Echocardiography showed akinetic anterior wall, septum, and apex, mild mitral regurgitation and ejection fraction of 45%. Coronary angiography revealed a saccular aneurysm of the left main coronary artery with significant stenosis in the left anterior descending, left circumflex, and right coronary artery. The patient immediately underwent coronary artery bypass grafting and ligation of the aneurysm. At six months’ follow-up, he remained asymptomatic. PMID:27403190

  6. Muon spin rotation studies

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The bulk of the muon spin rotation research work centered around the development of the muon spin rotation facility at the Alternating Gradient Synchrotron (AGS) of Brookhaven National Laboratory (BNL). The collimation system was both designed and fabricated at Virginia State University. This improved collimation system, plus improvements in detectors and electronics enabled the acquisition of spectra free of background out to 15 microseconds. There were two runs at Brookhaven in 1984, one run was devoted primarily to beam development and the other run allowed several successful experiments to be performed. The effect of uniaxial strain on an Fe(Si) crystal at elevated temperature (360K) was measured and the results are incorporated herein. A complete analysis of Fe pulling data taken earlier is included.

  7. Spinning superconducting electrovacuum soliton

    NASA Astrophysics Data System (ADS)

    Dymnikova, Irina

    2006-08-01

    In nonlinear electrodynamics coupled to general relativity and satisfying the weak energy condition, a spherically symmetric electrically charged electrovacuum soliton has obligatory de Sitter center in which the electric field vanishes while the energy density of electromagnetic vacuum achieves its maximal value. De Sitter vacuum supplies a particle with the finite positive electromagnetic mass related to breaking of space-time symmetry from the de Sitter group in the origin. By the Gürses-Gürsey algorithm based on the Newman-Trautman technique it is transformed into a spinning electrovacuum soliton asymptotically Kerr-Newman for a distant observer. De Sitter center becomes de Sitter equatorial disk which has both perfect conductor and ideal diamagnetic properties. The interior de Sitter vacuum disk displays superconducting behavior within a single spinning soliton. All this concerns both black hole and particle-like structures.

  8. Spin-driven inflation

    NASA Astrophysics Data System (ADS)

    Obukhov, Yuri N.

    1993-11-01

    Following recent studies of Ford, we suggest - in the framework of general relativity - an inflationary cosmological model with self-interacting spinning matter. A generalization of the standard fluid model is discussed and estimates of the physical parameters of the evolution are given. I would like to thank Professor Friedrich W. Hehl for the careful reading of the manuscript and useful advice. This research was supported by the Alexander von Humboldt Foundation (Bonn).

  9. Dusty spin plasmas

    SciTech Connect

    Brodin, G.; Marklund, M.; Zamanian, J.

    2008-09-07

    A fluid model is derived, taking into account the effect of spin magnetization of electrons as well as of magnetized dust grains. The model is analyzed, and it is found that both the acoustic velocity and the Alfven velocity is decreased due to the magnetization effects. Furthermore, for low-temperature high density plasmas, it is found that the linear wave modes can be unstable, due to the magnetic attraction of individual fluid elements. The significance of our results are discussed.

  10. Spin and gravitation

    NASA Technical Reports Server (NTRS)

    Ray, J. R.

    1982-01-01

    The fundamental variational principle for a perfect fluid in general relativity is extended so that it applies to the metric-torsion Einstein-Cartan theory. Field equations for a perfect fluid in the Einstein-Cartan theory are deduced. In addition, the equations of motion for a fluid with intrinsic spin in general relativity are deduced from a special relativistic variational principle. The theory is a direct extension of the theory of nonspinning fluids in special relativity.

  11. Left Subclavian Artery Occlusion: Femoro-Axillary Artery Retrograde Bypass

    PubMed Central

    Nakashima, Masaya; Kobayashi, Hideaki; Kobayashi, Masayoshi

    2016-01-01

    The treatment tactics for subclavian artery occlusion include the more commonly used endovascular therapy rather than surgical intervention. We present a case of a 61-year-old woman with dialysis-dependent chronic renal failure who experienced left finger necrosis in the left upper extremity. To salvage the limb, we performed femoro-axillary (fem-ax) artery bypass using an autologous saphenous vein graft. However, 10 months later, she experienced coldness in the left forearm. Angiography revealed chronic total occlusion of the venous bypass. Despite emergent thrombectomy, redo fem-ax artery bypass operation was performed using a prosthetic graft. Upper limb salvage can be achieved by fem-ax artery retrograde bypass. PMID:27386454

  12. Almanac 2015: coronary artery disease.

    PubMed

    Shavelle, David M

    2016-04-01

    Recent years have seen major advances in the evaluation and treatment of patients with coronary artery disease. These include assessment of novel biomarkers and imaging methods for patients at risk for coronary artery disease, care of patients with ST-segment elevation myocardial infarction, a novel device to treat medical refractory angina, use of non-statin lipid-lowering agents, a better understanding of the risks and benefits of long-term dual antiplatelet therapy and the use of the newer antiplatelet agents. This article summarises research related to coronary artery disease published in Heart in 2014 and 2015, within the context of other major cardiovascular journals. PMID:26819234

  13. Horizontal SPINning of transposons.

    PubMed

    Gilbert, Clément; Pace, John K; Feschotte, Cédric

    2009-01-01

    The term 'horizontal transfer (HT)' refers to the transfer of genetic material between two reproductively isolated organisms. HT is thought to occur rarely in eukaryotes compared to vertical inheritance, the transmission of DNA from parent to offspring. In a recent study we have provided evidence that a family of DNA transposons, called SPACE INVADERS or SPIN, independently invaded horizontally the genome of seven distantly related tetrapod species and subsequently amplified to high copy number in each of them. This discovery calls for further investigations to better characterize the extent to which genomes have been shaped through HT events. In this addendum, we briefly discuss some general issues regarding the study of HT and further speculate on the sequence of events that could explain the current taxonomic distribution of SPIN. We propose that the presence of SPIN in the opossum (Monodelphis domestica), a taxon endemic to South America, reflects a transoceanic HT event that occurred from Old to New World, between 46 and 15 million years ago.

  14. Nuclear spin circular dichroism

    SciTech Connect

    Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

    2014-04-07

    Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra.

  15. Pancreaticoduodenal Artery Aneurysm Formation with Superior Mesenteric Artery Stenosis

    PubMed Central

    Kitaoka, Tadashi; Kamiya, Chiaki; Suzuki, Jun; Sato, Osamu

    2014-01-01

    Celiac stenosis or occlusion is attributed partly to increase blood flow at pancreatic arcade from the superior mesenteric artery (SMA) system and may play a causal role in true aneurysm of pancreaticoduodenal artery (PDAA) formation. However, despite possible increased blood flow in the pancreatic arcades like celiac stenosis, PDAAs with a stenotic SMA are extremely rare, with only three cases have been reported in the literature. We report a case of PDAA with SMA stenosis and review the literature. PMID:25298835

  16. Spin-bus concept of spin quantum computing

    SciTech Connect

    Mehring, Michael; Mende, Jens

    2006-05-15

    We present a spin-bus concept of quantum computing where an electron spin S=1/2 acts as a bus qubit connected to a finite number N of nuclear spins I=1/2 serving as client qubits. Spin-bus clusters are considered as local processing units and may be interconnected with other spin-bus clusters via electron-electron coupling in a scaled up version. Here we lay the ground for the basic functional unit with long qubit registers, provide the theory and experimental verification of correlated qubit states, and demonstrate the Deutsch algorithm. Experiments were performed on a qubyte plus one nuclear spin in a solid state system.

  17. FAST AND EXACT SPIN-s SPHERICAL HARMONIC TRANSFORMS

    SciTech Connect

    Huffenberger, Kevin M.; Wandelt, Benjamin D.

    2010-08-15

    We demonstrate a fast spin-s spherical harmonic transform algorithm, which is flexible and exact for band-limited functions. In contrast to previous work, where spin transforms are computed independently, our algorithm permits the computation of several distinct spin transforms simultaneously. Specifically, only one set of special functions is computed for transforms of quantities with any spin, namely the Wigner d matrices evaluated at {pi}/2, which may be computed with efficient recursions. For any spin, the computation scales as O(L{sup 3}), where L is the band limit of the function. Our publicly available numerical implementation permits very high accuracy at modest computational cost. We discuss applications to the cosmic microwave background and gravitational lensing.

  18. Coherent spin mixing dynamics in a spin-1 atomic condensate

    SciTech Connect

    Zhang Wenxian; Chang, M.-S.; Chapman, M.S.; Zhou, D.L.; You, L.

    2005-07-15

    We study the coherent off-equilibrium spin mixing inside an atomic condensate. Using mean-field theory and adopting the single-spatial-mode approximation, the condensate spin dynamics is found to be well described by that of a nonrigid pendulum and displays a variety of periodic oscillations in an external magnetic field. Our results illuminate several recent experimental observations and provide critical insights into the observation of coherent interaction-driven oscillations in a spin-1 condensate.

  19. Pulmonary arterial hypertension

    PubMed Central

    2013-01-01

    Pulmonary arterial hypertension (PAH) is a chronic and progressive disease leading to right heart failure and ultimately death if untreated. The first classification of PH was proposed in 1973. In 2008, the fourth World Symposium on PH held in Dana Point (California, USA) revised previous classifications. Currently, PH is devided into five subgroups. Group 1 includes patients suffering from idiopathic or familial PAH with or without germline mutations. Patients with a diagnosis of PAH should systematically been screened regarding to underlying mutations of BMPR2 gene (bone morphogenetic protein receptor type 2) or more rarely of ACVRL1 (activine receptor-like kinase type 1), ENG (endogline) or Smad8 genes. Pulmonary veno occusive disease and pulmonary capillary hemagiomatosis are individualized and designated as clinical group 1'. Group 2 'Pulmonary hypertension due to left heart diseases' is divided into three sub-groups: systolic dysfonction, diastolic dysfonction and valvular dysfonction. Group 3 'Pulmonary hypertension due to respiratory diseases' includes a heterogenous subgroup of respiratory diseases like PH due to pulmonary fibrosis, COPD, lung emphysema or interstitial lung disease for exemple. Group 4 includes chronic thromboembolic pulmonary hypertension without any distinction of proximal or distal forms. Group 5 regroup PH patients with unclear multifactorial mechanisms. Invasive hemodynamic assessment with right heart catheterization is requested to confirm the definite diagnosis of PH showing a resting mean pulmonary artery pressure (mPAP) of ≥ 25 mmHg and a normal pulmonary capillary wedge pressure (PCWP) of ≤ 15 mmHg. The assessment of PCWP may allow the distinction between pre-capillary and post-capillary PH (PCWP > 15 mmHg). Echocardiography is an important tool in the management of patients with underlying suspicion of PH. The European Society of Cardiology and the European Respiratory Society (ESC-ERS) guidelines specify its role

  20. Pulmonary arterial hypertension.

    PubMed

    Montani, David; Günther, Sven; Dorfmüller, Peter; Perros, Frédéric; Girerd, Barbara; Garcia, Gilles; Jaïs, Xavier; Savale, Laurent; Artaud-Macari, Elise; Price, Laura C; Humbert, Marc; Simonneau, Gérald; Sitbon, Olivier

    2013-01-01

    Pulmonary arterial hypertension (PAH) is a chronic and progressive disease leading to right heart failure and ultimately death if untreated. The first classification of PH was proposed in 1973. In 2008, the fourth World Symposium on PH held in Dana Point (California, USA) revised previous classifications. Currently, PH is devided into five subgroups. Group 1 includes patients suffering from idiopathic or familial PAH with or without germline mutations. Patients with a diagnosis of PAH should systematically been screened regarding to underlying mutations of BMPR2 gene (bone morphogenetic protein receptor type 2) or more rarely of ACVRL1 (activine receptor-like kinase type 1), ENG (endogline) or Smad8 genes. Pulmonary veno occusive disease and pulmonary capillary hemagiomatosis are individualized and designated as clinical group 1'. Group 2 'Pulmonary hypertension due to left heart diseases' is divided into three sub-groups: systolic dysfonction, diastolic dysfonction and valvular dysfonction. Group 3 'Pulmonary hypertension due to respiratory diseases' includes a heterogenous subgroup of respiratory diseases like PH due to pulmonary fibrosis, COPD, lung emphysema or interstitial lung disease for exemple. Group 4 includes chronic thromboembolic pulmonary hypertension without any distinction of proximal or distal forms. Group 5 regroup PH patients with unclear multifactorial mechanisms. Invasive hemodynamic assessment with right heart catheterization is requested to confirm the definite diagnosis of PH showing a resting mean pulmonary artery pressure (mPAP) of ≥ 25 mmHg and a normal pulmonary capillary wedge pressure (PCWP) of ≤ 15 mmHg. The assessment of PCWP may allow the distinction between pre-capillary and post-capillary PH (PCWP > 15 mmHg). Echocardiography is an important tool in the management of patients with underlying suspicion of PH. The European Society of Cardiology and the European Respiratory Society (ESC-ERS) guidelines specify its role

  1. Signs and Symptoms of Artery Disease | Coronary Artery Disease | NIH MedlinePlus the Magazine

    MedlinePlus

    ... this page please turn Javascript on. Feature: Coronary Artery Disease Signs and Symptoms of Artery Disease Past Issues / Fall 2010 Table of Contents ... this depends on which arteries are affected. Coronary Arteries Coronary arteries supply oxygen-rich blood to the ...

  2. Decoupling a hole spin qubit from the nuclear spins

    NASA Astrophysics Data System (ADS)

    Prechtel, Jonathan H.; Kuhlmann, Andreas V.; Houel, Julien; Ludwig, Arne; Valentin, Sascha R.; Wieck, Andreas D.; Warburton, Richard J.

    2016-09-01

    A huge effort is underway to develop semiconductor nanostructures as low-noise hosts for qubits. The main source of dephasing of an electron spin qubit in a GaAs-based system is the nuclear spin bath. A hole spin may circumvent the nuclear spin noise. In principle, the nuclear spins can be switched off for a pure heavy-hole spin. In practice, it is unknown to what extent this ideal limit can be achieved. A major hindrance is that p-type devices are often far too noisy. We investigate here a single hole spin in an InGaAs quantum dot embedded in a new generation of low-noise p-type device. We measure the hole Zeeman energy in a transverse magnetic field with 10 neV resolution by dark-state spectroscopy as we create a large transverse nuclear spin polarization. The hole hyperfine interaction is highly anisotropic: the transverse coupling is <1% of the longitudinal coupling. For unpolarized, randomly fluctuating nuclei, the ideal heavy-hole limit is achieved down to nanoelectronvolt energies; equivalently dephasing times up to a microsecond. The combination of large and strong optical dipole makes the single hole spin in a GaAs-based device an attractive quantum platform.

  3. Correlation functions of the integrable spin-s chain

    NASA Astrophysics Data System (ADS)

    Ribeiro, G. A. P.; Klümper, A.

    2016-06-01

    We study the correlation functions of su(2) invariant spin-s chains in the thermodynamic limit. We derive nonlinear integral equations for an auxiliary correlation function ω for any spin s and finite temperature T. For the spin-3/2 chain for arbitrary temperature and zero magnetic field we obtain algebraic expressions for the reduced density matrix of two-sites. In the zero temperature limit, the density matrix elements are evaluated analytically and appear to be given in terms of Riemann’s zeta function values of even and odd arguments. Dedicated to Professor Rodney Baxter on the occasion of his 75th birthday.

  4. Chiral spin liquids in arrays of spin chains

    NASA Astrophysics Data System (ADS)

    Gorohovsky, Gregory; Pereira, Rodrigo G.; Sela, Eran

    2015-06-01

    We describe a coupled-chain construction for chiral spin liquids in two-dimensional spin systems. Starting from a one-dimensional zigzag spin chain and imposing SU(2) symmetry in the framework of non-Abelian bosonization, we first show that our approach faithfully describes the low-energy physics of an exactly solvable model with a three-spin interaction. Generalizing the construction to the two-dimensional case, we obtain a theory that incorporates the universal properties of the chiral spin liquid predicted by Kalmeyer and Laughlin: charge-neutral edge states, gapped spin-1/2 bulk excitations, and ground-state degeneracy on the torus signaling the topological order of this quantum state. In addition, we show that the chiral spin liquid phase is more easily stabilized in frustrated lattices containing corner-sharing triangles, such as the extended kagome lattice, than in the triangular lattice. Our field-theoretical approach invites generalizations to more exotic chiral spin liquids and may be used to assess the existence of the chiral spin liquid as the ground state of specific lattice systems.

  5. Valley-spin blockade and spin resonance in carbon nanotubes.

    PubMed

    Pei, Fei; Laird, Edward A; Steele, Gary A; Kouwenhoven, Leo P

    2012-10-01

    The manipulation and readout of spin qubits in quantum dots have been successfully achieved using Pauli blockade, which forbids transitions between spin-triplet and spin-singlet states. Compared with spin qubits realized in III-V materials, group IV materials such as silicon and carbon are attractive for this application because of their low decoherence rates (nuclei with zero spins). However, valley degeneracies in the electronic band structure of these materials combined with Coulomb interactions reduce the energy difference between the blocked and unblocked states, significantly weakening the selection rules for Pauli blockade. Recent demonstrations of spin qubits in silicon devices have required strain and spatial confinement to lift the valley degeneracy. In carbon nanotubes, Pauli blockade can be observed by lifting valley degeneracy through disorder, but this makes the confinement potential difficult to control. To achieve Pauli blockade in low-disorder nanotubes, quantum dots have to be made ultrasmall, which is incompatible with conventional fabrication methods. Here, we exploit the bandgap of low-disorder nanotubes to demonstrate robust Pauli blockade based on both valley and spin selection rules. We use a novel stamping technique to create a bent nanotube, in which single-electron spin resonance is detected using the blockade. Our results indicate the feasibility of valley-spin qubits in carbon nanotubes.

  6. Pregnancy-related rupture of arterial aneurysms.

    PubMed

    Barrett, J M; Van Hooydonk, J E; Boehm, F H

    1982-09-01

    Over 50 per cent of ruptured arterial aneurysms in women under the age of 40 are pregnancy-related. The hemodynamic and endocrine changes of pregnancy appear to be the cause of arterial alterations which may lead to new aneurysm formation and/or weakening of preexisting aneurysms. The most commonly reported arteries to have aneurysms rupture during pregnancy are the aorta, cerebral arteries, splenic artery, renal artery, coronary artery, and ovarian artery. In many instances, the rupture of an arterial aneurysm will initially simulate other less serious disease processes, thus delaying the correct diagnosis until a catastrophic event occurs. Early diagnosis and treatment of a ruptured arterial aneurysm are imperative in order to give optimal chances of survival to the mother and fetus.

  7. Cineangiography of the Coronary Arteries

    PubMed Central

    Tremblay, Gerard M.; Charland, Raymond; Roy, Paul; Primeau, Robert; Nadeau, Reginald

    1971-01-01

    Fifty French-Canadian patients presenting with typical or atypical anginal pain were studied by selective cinearteriography and coronary sinus catheterization, with measurement of myocardial function, oxygen and lactate extraction at rest and during isoproterenol infusion. In 28 of 42 patients all three coronary arteries were involved, but angina pectoris also occurred in patients with single mildly stenotic arterial lesions and even in eight patients with normal cinearteriograms. All patients with severe arterial lesions had typical angina, and the longer the duration of angina, the greater the extent, usually, of anatomic disease. Seventy-nine percent of resting electrocardiograms of patients with documented coronary artery disease were abnormal, with recognizable prior infarction in 18. Two-thirds of the patients experiencing pain during the stressful state had abnormal ventricular function. An abnormal arteriovenous lactate difference in response to isoproterenol occurred in patients in all groups. PMID:5563346

  8. Peripheral artery bypass - leg - discharge

    MedlinePlus

    ... P. Peripheral arterial diseases. In: Mann DL, Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's ... noncoronary obstructive vascular disease. In: Mann DL, Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's ...

  9. [The arteries of the stomach].

    PubMed

    Sow, M L; Diop, M; Morin, A

    1995-06-01

    In order to specify the gastric-arterial systematization, 65 fresh stomachs of adults deceased from non-gastro-duodenal causes, extracted by necropsy, allowed us to study the arteries of the stomach through the injection-corrosion technics. A selective injection for each arterial trunk has been made on 15 stomachs. This work allowed us to know better the arterial supply of the stomach and ut into obviousness important vascular anastomosis. While emphasizing on the substitute notion, the persons who wrote this summary describe regions poor in anastomosis, which correspond surgically with "critical" areas. They also emphasize how important it is to have an estimated score of the ischemia for gastric surgery, especially in the case of oeso-gastroplasty.

  10. [Doppler ultrasound of penis arteries].

    PubMed

    Jünemann, K P; Siegsmund, M; Löbelenz, M; Alken, P

    1990-05-01

    In addition to pharmaco testing, pharmaco-Doppler sonography of the penile arteries is part of the basic work-up for erectile dysfunction. Insufficient training with the Doppler method, lack of standardized criteria for evaluation of the penis, and analysis of the Doppler curves all make it difficult to use Doppler sonography for the evaluation of impotent men. The aim of this study was to explain the principal criteria of the method and demonstrate the most important details for analyzing the form of the Doppler waves. Pharmaco-Doppler sonography includes the evaluation of blood-flow velocities within the dorsal and deep cavernous arteries of the penis before and after intracavernous application of a vasoactive drug. The following main criteria have proven to be most important for analysis of the Doppler curves: evaluation of the amplitude height, the actual wave form, differences between the left and right arteries and along the individual vessel, amplitude increase, and elevation of the curve baseline after pharmaco stimulation. The most frequent mistakes made during evaluation of the penile arteries are changes in the probe angle, pressure put on the artery by the probe during evaluation and a false estimation of the evaluation time after pharmaco stimulation. Recently, duplex sonography of the penile arteries has been introduced, and this method allows an accurate measurement of the blood-flow velocity and arterial diameter changes before and after application of the drug. Furthermore, additional calculation of the resistancy index permits determination of the vascular resistance and optimizes the evaluation of the penile arterial status. The technical details, the method, and the analyzation criteria are all explained in detail.

  11. Semicircular Rashba arc spin polarizer

    SciTech Connect

    Bin Siu, Zhuo; Jalil, Mansoor B. A.; Ghee Tan, Seng

    2014-05-07

    In this work, we study the generation of spin polarized currents using curved arcs of finite widths, in which the Rashba spin orbit interaction (RSOI) is present. Compared to the 1-dimensional RSOI arcs with zero widths studied previously, the finite width presents charge carriers with another degree of freedom along the transverse width of the arc, in addition to the longitudinal degree of freedom along the circumference of the arc. The asymmetry in the transverse direction due to the difference in the inner and outer radii of the arc breaks the antisymmetry of the longitudinal spin z current in a straight RSOI segment. This property can be exploited to generate spin z polarized current output from the RSOI arc by a spin unpolarized current input. The sign of the spin current can be manipulated by varying the arc dimensions.

  12. Inductance due to spin current

    SciTech Connect

    Chen, Wei

    2014-03-21

    The inductance of spintronic devices that transport charge neutral spin currents is discussed. It is known that in a media that contains charge neutral spins, a time-varying electric field induces a spin current. We show that since the spin current itself produces an electric field, this implies existence of inductance and electromotive force when the spin current changes with time. The relations between the electromotive force and the corresponding flux, which is a vector calculated by the cross product of electric field and the trajectory of the device, are clarified. The relativistic origin generally renders an extremely small inductance, which indicates the advantage of spin current in building low inductance devices. The same argument also explains the inductance due to electric dipole current and applies to physical dipoles consist of polarized bound charges.

  13. Spin heat accumulation and spin-dependent temperatures in nanopillar spin valves

    NASA Astrophysics Data System (ADS)

    Dejene, F. K.; Flipse, J.; Bauer, G. E. W.; van Wees, B. J.

    2013-10-01

    Since the discovery of the giant magnetoresistance effect the intrinsic angular momentum of the electron has opened up new spin-based device concepts. Our present understanding of the coupled transport of charge, spin and heat relies on the two-channel model for spin-up and spin-down electrons having equal temperatures. Here we report the observation of different (effective) temperatures for the spin-up and spin-down electrons in a nanopillar spin valve subject to a heat current. By three-dimensional finite element modelling of our devices for varying thickness of the non-magnetic layer, spin heat accumulations (the difference of the spin temperatures) of 120mK and 350mK are extracted at room temperature and 77K, respectively, which is of the order of 10% of the total temperature bias over the nanopillar. This technique uniquely allows the study of inelastic spin scattering at low energies and elevated temperatures, which is not possible by spectroscopic methods.

  14. Ruptured Isolated Spinal Artery Aneurysms

    PubMed Central

    Gutierrez Romero, Diego; Batista, Andre Lima; Gentric, Jean Christoph; Raymond, Jean; Roy, Daniel; Weill, Alain

    2014-01-01

    Summary Isolated spinal artery aneurysms are exceedingly rare vascular lesions thought to be related to dissection of the arterial wall. We describe two cases presenting with spinal subarachnoid haemorrhage that underwent conservative management. In the first patient the radiculomedullary branch involved was feeding the anterior spinal artery at the level of D3 and thus, neither endovascular nor surgical approach was employed. Control angiography was performed at seven days and at three months, demonstrating complete resolution of the lesion. In our second case, neither the anterior spinal artery or the artery of Adamkiewicz could be identified during angiography, thus endovascular management was deemed contraindicated. Magnetic resonance imaging showed a stable lesion in the second patient. No rebleeding or other complications were seen. In comparison to intracranial aneurysms, spinal artery aneurysms tend to display a fusiform appearance and lack a clear neck in relation to the likely dissecting nature of the lesions. Due to the small number of cases reported, the natural history of these lesions is not well known making it difficult to establish the optimal treatment approach. Various management strategies may be supported, including surgical and endovascular treatment, but It would seem that a wait and see approach is also viable, with control angiogram and treatment decisions based on the evolution of the lesion. PMID:25496690

  15. Arterial Stiffness and Cardiovascular Therapy

    PubMed Central

    Janić, Miodrag; Lunder, Mojca; Šabovič, Mišo

    2014-01-01

    The world population is aging and the number of old people is continuously increasing. Arterial structure and function change with age, progressively leading to arterial stiffening. Arterial stiffness is best characterized by measurement of pulse wave velocity (PWV), which is its surrogate marker. It has been shown that PWV could improve cardiovascular event prediction in models that included standard risk factors. Consequently, it might therefore enable better identification of populations at high-risk of cardiovascular morbidity and mortality. The present review is focused on a survey of different pharmacological therapeutic options for decreasing arterial stiffness. The influence of several groups of drugs is described: antihypertensive drugs (angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, beta-blockers, diuretics, and nitrates), statins, peroral antidiabetics, advanced glycation end-products (AGE) cross-link breakers, anti-inflammatory drugs, endothelin-A receptor antagonists, and vasopeptidase inhibitors. All of these have shown some effect in decreasing arterial stiffness. Nevertheless, further studies are needed which should address the influence of arterial stiffness diminishment on major adverse cardiovascular and cerebrovascular events (MACCE). PMID:25170513

  16. Parameters of spinning FM reticles.

    PubMed

    Driggers, R G; Halford, C E; Boreman, G D; Lattman, D; Williams, K F

    1991-03-01

    The literature describes tracking devices that allow a single detector coupled to a spinning FM reticle to determine target location. The spinning FM reticles presented were limited to single parameter reticles of frequency vs angle, frequency vs radius, or phase. This study presents these parameters with their capabilities and limitations and shows that multiple parameters can be integrated into a single reticle. Also, a general equation is developed that describes any FM reticle of the spinning type. PMID:20582075

  17. Understanding the proton's spin structure

    SciTech Connect

    Fred Myhrer; Thomas, Anthony W.

    2010-02-01

    We discuss the tremendous progress that has been towards an understanding of how the spin of the proton is distributed on its quark and gluon constituents. This is a problem that began in earnest twenty years ago with the discovery of the proton "spin crisis" by the European Muon Collaboration. The discoveries prompted by that original work have given us unprecedented insight into the amount of spin carried by polarized gluons and the orbital angular momentum of the quarks.

  18. 14 CFR 23.221 - Spinning.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Spinning. 23.221 Section 23.221 Aeronautics... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Flight Spinning § 23.221 Spinning. (a...-turn spin or a three-second spin, whichever takes longer, in not more than one additional turn...

  19. 14 CFR 23.221 - Spinning.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Spinning. 23.221 Section 23.221 Aeronautics... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Flight Spinning § 23.221 Spinning. (a...-turn spin or a three-second spin, whichever takes longer, in not more than one additional turn...

  20. 14 CFR 23.221 - Spinning.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Spinning. 23.221 Section 23.221 Aeronautics... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Flight Spinning § 23.221 Spinning. (a...-turn spin or a three-second spin, whichever takes longer, in not more than one additional turn...

  1. The straintronic spin-neuron.

    PubMed

    Biswas, Ayan K; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-07-17

    In artificial neural networks, neurons are usually implemented with highly dissipative CMOS-based operational amplifiers. A more energy-efficient implementation is a 'spin-neuron' realized with a magneto-tunneling junction (MTJ) that is switched with a spin-polarized current (representing weighted sum of input currents) that either delivers a spin transfer torque or induces domain wall motion in the soft layer of the MTJ to mimic neuron firing. Here, we propose and analyze a different type of spin-neuron in which the soft layer of the MTJ is switched with mechanical strain generated by a voltage (representing weighted sum of input voltages) and term it straintronic spin-neuron. It dissipates orders of magnitude less energy in threshold operations than the traditional current-driven spin neuron at 0 K temperature and may even be faster. We have also studied the room-temperature firing behaviors of both types of spin neurons and find that thermal noise degrades the performance of both types, but the current-driven type is degraded much more than the straintronic type if both are optimized for maximum energy-efficiency. On the other hand, if both are designed to have the same level of thermal degradation, then the current-driven version will dissipate orders of magnitude more energy than the straintronic version. Thus, the straintronic spin-neuron is superior to current-driven spin neurons. PMID:26112081

  2. Alkali-Metal Spin Maser.

    PubMed

    Chalupczak, W; Josephs-Franks, P

    2015-07-17

    Quantum measurement is a combination of a read-out and a perturbation of the quantum system. We explore the nonlinear spin dynamics generated by a linearly polarized probe beam in a continuous measurement of the collective spin state in a thermal alkali-metal atomic sample. We demonstrate that the probe-beam-driven perturbation leads, in the presence of indirect pumping, to complete polarization of the sample and macroscopic coherent spin oscillations. As a consequence of the former we report observation of spectral profiles free from collisional broadening. Nonlinear dynamics is studied through exploring its effect on radio frequency as well as spin noise spectra. PMID:26230788

  3. The straintronic spin-neuron

    NASA Astrophysics Data System (ADS)

    Biswas, Ayan K.; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-07-01

    In artificial neural networks, neurons are usually implemented with highly dissipative CMOS-based operational amplifiers. A more energy-efficient implementation is a ‘spin-neuron’ realized with a magneto-tunneling junction (MTJ) that is switched with a spin-polarized current (representing weighted sum of input currents) that either delivers a spin transfer torque or induces domain wall motion in the soft layer of the MTJ to mimic neuron firing. Here, we propose and analyze a different type of spin-neuron in which the soft layer of the MTJ is switched with mechanical strain generated by a voltage (representing weighted sum of input voltages) and term it straintronic spin-neuron. It dissipates orders of magnitude less energy in threshold operations than the traditional current-driven spin neuron at 0 K temperature and may even be faster. We have also studied the room-temperature firing behaviors of both types of spin neurons and find that thermal noise degrades the performance of both types, but the current-driven type is degraded much more than the straintronic type if both are optimized for maximum energy-efficiency. On the other hand, if both are designed to have the same level of thermal degradation, then the current-driven version will dissipate orders of magnitude more energy than the straintronic version. Thus, the straintronic spin-neuron is superior to current-driven spin neurons.

  4. The straintronic spin-neuron.

    PubMed

    Biswas, Ayan K; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-07-17

    In artificial neural networks, neurons are usually implemented with highly dissipative CMOS-based operational amplifiers. A more energy-efficient implementation is a 'spin-neuron' realized with a magneto-tunneling junction (MTJ) that is switched with a spin-polarized current (representing weighted sum of input currents) that either delivers a spin transfer torque or induces domain wall motion in the soft layer of the MTJ to mimic neuron firing. Here, we propose and analyze a different type of spin-neuron in which the soft layer of the MTJ is switched with mechanical strain generated by a voltage (representing weighted sum of input voltages) and term it straintronic spin-neuron. It dissipates orders of magnitude less energy in threshold operations than the traditional current-driven spin neuron at 0 K temperature and may even be faster. We have also studied the room-temperature firing behaviors of both types of spin neurons and find that thermal noise degrades the performance of both types, but the current-driven type is degraded much more than the straintronic type if both are optimized for maximum energy-efficiency. On the other hand, if both are designed to have the same level of thermal degradation, then the current-driven version will dissipate orders of magnitude more energy than the straintronic version. Thus, the straintronic spin-neuron is superior to current-driven spin neurons.

  5. Alkali-Metal Spin Maser

    NASA Astrophysics Data System (ADS)

    Chalupczak, W.; Josephs-Franks, P.

    2015-07-01

    Quantum measurement is a combination of a read-out and a perturbation of the quantum system. We explore the nonlinear spin dynamics generated by a linearly polarized probe beam in a continuous measurement of the collective spin state in a thermal alkali-metal atomic sample. We demonstrate that the probe-beam-driven perturbation leads, in the presence of indirect pumping, to complete polarization of the sample and macroscopic coherent spin oscillations. As a consequence of the former we report observation of spectral profiles free from collisional broadening. Nonlinear dynamics is studied through exploring its effect on radio frequency as well as spin noise spectra.

  6. RHIC spin program

    SciTech Connect

    Bunce, G.

    1995-12-31

    Colliding beams of high energy polarized protons at RHIC is an excellent way to probe the polarization of gluons, u and d quarks in a polarized proton. RHIC is the Relativistic Heavy Ion Collider being built now at Brookhaven in the ISABELLE tunnel. It is designed to collide gold ions on gold ions at 100 GeV/nucleon. Its goal is to discover the quark-gluon plasma, and the first collisions are expected in March, 1999. RHIC will also make an ideal polarized proton collider with high luminosity and 250 GeV x 250 GeV collisions. The RHIC spin physics program is: (1) Use well-understood perturbative QCD probes to study non-perturbative confining dynamics in QCD. We will measure - gluon and sea quark polarization in a polarized proton, polarization of quarks in a transversely polarized proton. (2) Look for additional surprises using the first high energy polarized proton collider. We will - look for the expected maximal parity violation in W and Z boson production, - search for parity violation in other processes, - test parton models with spin. This lecture is organized around a few of the key ideas: Siberian Snakes--What are they? High energy proton-proton collisions are scatters of quarks and leptons, at high x, a polarized proton beam is a beam of polarized u quarks, quark and gluon collisions are very sensitive to spin. We will discuss two reactions: how direct photon production measures gluon polarization, and how W{sup +} boson production measures u and d quark polarization.

  7. Coronary Artery Disease | Coronary Artery Disease | NIH MedlinePlus the Magazine

    MedlinePlus

    ... this page please turn Javascript on. Feature: Coronary Artery Disease Coronary Artery Disease Past Issues / Fall 2010 Table of Contents ... exercise routine produced a strong heart!" Fast Facts Arteries are blood vessels that carry oxygen-rich blood ...

  8. Recurrent ischemia resulting from left internal mammary artery-to-pulmonary artery fistula.

    PubMed

    Madu, E C; Hanumanthu, S K; Kim, C; Prudoff, A

    2001-03-01

    This report describes a case series of recurrent ischemia after coronary artery bypass grafting resulting from left internal mammary artery-to-pulmonary artery fistula. An angiographic demonstration of this fistula is presented.

  9. Spin-Hall effect and spin-Coulomb drag in doped semiconductors.

    PubMed

    Hankiewicz, E M; Vignale, G

    2009-06-24

    In this review, we describe in detail two important spin-transport phenomena: the extrinsic spin-Hall effect (coming from spin-orbit interactions between electrons and impurities) and the spin-Coulomb drag. The interplay of these two phenomena is analyzed. In particular, we discuss the influence of scattering between electrons with opposite spins on the spin current and the spin accumulation produced by the spin-Hall effect. Future challenges and open questions are briefly discussed.

  10. TOPICAL REVIEW: Spin-Hall effect and spin-Coulomb drag in doped semiconductors

    NASA Astrophysics Data System (ADS)

    Hankiewicz, E. M.; Vignale, G.

    2009-06-01

    In this review, we describe in detail two important spin-transport phenomena: the extrinsic spin-Hall effect (coming from spin-orbit interactions between electrons and impurities) and the spin-Coulomb drag. The interplay of these two phenomena is analyzed. In particular, we discuss the influence of scattering between electrons with opposite spins on the spin current and the spin accumulation produced by the spin-Hall effect. Future challenges and open questions are briefly discussed.

  11. Spin resonance strength calculations

    SciTech Connect

    Courant,E.D.

    2008-10-06

    In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.

  12. Spin waves in the (

    SciTech Connect

    Lipscombe, O. J.; Chen, G. F.; Fang, Chen; Perring, T. G.; Abernathy, Douglas L; Christianson, Andrew D; Egami, Takeshi; Wang, Nanlin; Hu, Jiangping; Dai, Pengcheng

    2011-01-01

    We use neutron scattering to show that spin waves in the iron chalcogenide Fe{sub 1.05}Te display novel dispersion clearly different from both the first principles density functional calculations and recent observations in the related iron pnictide CaFe{sub 2}As{sub 2}. By fitting to a Heisenberg Hamiltonian, we find that although the nearest-neighbor exchange couplings in the two systems are quite different, their next-nearest-neighbor (NNN) couplings are similar. This suggests that superconductivity in the pnictides and chalcogenides share a common magnetic origin that is intimately associated with the NNN magnetic coupling between the irons.

  13. The hepatic artery in liver transplantation.

    PubMed

    Merion, R M; Burtch, G D; Ham, J M; Turcotte, J G; Campbell, D A

    1989-09-01

    Hepatic artery complications after liver transplantation are uncommon, but represent an important cause of morbidity and mortality. In addition, these complications tax an already limited supply of donor organs because of the frequent need for retransplantation in this group of patients. In this study, we examined the incidence of hepatic arterial anomalies in donors and recipients of orthotopic liver transplants, focusing on the techniques that are available for hepatic arterial reconstruction and on the occurrence of hepatic arterial complications. A total of 77 liver transplants were carried out in 68 patients. Standard recipient anatomy was present in 60 of 68 patients (88%). Anomalous vessels were identified in eight patients (12%), including six cases of replaced right hepatic artery (9%) and two cases of replaced left hepatic artery (3%). Donor liver arterial anatomy was standard in 62 cases (80%). Anomalous arterial supply was identified in 15 of 77 donor livers (20%), including replaced left hepatic artery in nine (12%) and replaced right hepatic artery in six (8%). A variety of methods were used to manage the anomalous vessels. There was one hepatic artery pseudoaneurysm, three cases of hepatic artery thrombosis (4%), and one patient developed a dissection of the native celiac axis. In primary transplants, utilization of the recipient's proper hepatic artery was associated with a significantly higher risk of hepatic artery thrombosis (P less than 0.04) when compared with the common hepatic artery or the branch patch technique. Use of a Carrel patch on the donor artery was associated with a significantly reduced incidence of hepatic artery thrombosis (P less than 0.0003). For retransplantation, it is recommended that a more proximal recipient anastomotic site be chosen. An innovative method is described that provides increased length of the donor arterial supply without the use of an arterial graft. PMID:2675403

  14. Feasibility of Quantifying Arterial Cerebral Blood Volume Using Multiphase Alternate Ascending/Descending Directional Navigation (ALADDIN)

    PubMed Central

    Kim, Ki Hwan; Choi, Seung Hong; Park, Sung-Hong

    2016-01-01

    Arterial cerebral blood volume (aCBV) is associated with many physiologic and pathologic conditions. Recently, multiphase balanced steady state free precession (bSSFP) readout was introduced to measure labeled blood signals in the arterial compartment, based on the fact that signal difference between labeled and unlabeled blood decreases with the number of RF pulses that is affected by blood velocity. In this study, we evaluated the feasibility of a new 2D inter-slice bSSFP-based arterial spin labeling (ASL) technique termed, alternate ascending/descending directional navigation (ALADDIN), to quantify aCBV using multiphase acquisition in six healthy subjects. A new kinetic model considering bSSFP RF perturbations was proposed to describe the multiphase data and thus to quantify aCBV. Since the inter-slice time delay (TD) and gap affected the distribution of labeled blood spins in the arterial and tissue compartments, we performed the experiments with two TDs (0 and 500 ms) and two gaps (300% and 450% of slice thickness) to evaluate their roles in quantifying aCBV. Comparison studies using our technique and an existing method termed arterial volume using arterial spin tagging (AVAST) were also separately performed in five subjects. At 300% gap or 500-ms TD, significant tissue perfusion signals were demonstrated, while tissue perfusion signals were minimized and arterial signals were maximized at 450% gap and 0-ms TD. ALADDIN has an advantage of visualizing bi-directional flow effects (ascending/descending) in a single experiment. Labeling efficiency (α) of inter-slice blood flow effects could be measured in the superior sagittal sinus (SSS) (20.8±3.7%.) and was used for aCBV quantification. As a result of fitting to the proposed model, aCBV values in gray matter (1.4–2.3 mL/100 mL) were in good agreement with those from literature. Our technique showed high correlation with AVAST, especially when arterial signals were accentuated (i.e., when TD = 0 ms) (r = 0

  15. Feasibility of Quantifying Arterial Cerebral Blood Volume Using Multiphase Alternate Ascending/Descending Directional Navigation (ALADDIN).

    PubMed

    Kim, Ki Hwan; Choi, Seung Hong; Park, Sung-Hong

    2016-01-01

    Arterial cerebral blood volume (aCBV) is associated with many physiologic and pathologic conditions. Recently, multiphase balanced steady state free precession (bSSFP) readout was introduced to measure labeled blood signals in the arterial compartment, based on the fact that signal difference between labeled and unlabeled blood decreases with the number of RF pulses that is affected by blood velocity. In this study, we evaluated the feasibility of a new 2D inter-slice bSSFP-based arterial spin labeling (ASL) technique termed, alternate ascending/descending directional navigation (ALADDIN), to quantify aCBV using multiphase acquisition in six healthy subjects. A new kinetic model considering bSSFP RF perturbations was proposed to describe the multiphase data and thus to quantify aCBV. Since the inter-slice time delay (TD) and gap affected the distribution of labeled blood spins in the arterial and tissue compartments, we performed the experiments with two TDs (0 and 500 ms) and two gaps (300% and 450% of slice thickness) to evaluate their roles in quantifying aCBV. Comparison studies using our technique and an existing method termed arterial volume using arterial spin tagging (AVAST) were also separately performed in five subjects. At 300% gap or 500-ms TD, significant tissue perfusion signals were demonstrated, while tissue perfusion signals were minimized and arterial signals were maximized at 450% gap and 0-ms TD. ALADDIN has an advantage of visualizing bi-directional flow effects (ascending/descending) in a single experiment. Labeling efficiency (α) of inter-slice blood flow effects could be measured in the superior sagittal sinus (SSS) (20.8±3.7%.) and was used for aCBV quantification. As a result of fitting to the proposed model, aCBV values in gray matter (1.4-2.3 mL/100 mL) were in good agreement with those from literature. Our technique showed high correlation with AVAST, especially when arterial signals were accentuated (i.e., when TD = 0 ms) (r = 0

  16. Spin-SILC: CMB polarisation component separation with spin wavelets

    NASA Astrophysics Data System (ADS)

    Rogers, Keir K.; Peiris, Hiranya V.; Leistedt, Boris; McEwen, Jason D.; Pontzen, Andrew

    2016-08-01

    We present Spin-SILC, a new foreground component separation method that accurately extracts the cosmic microwave background (CMB) polarisation E and B modes from raw multifrequency Stokes Q and U measurements of the microwave sky. Spin-SILC is an internal linear combination method that uses spin wavelets to analyse the spin-2 polarisation signal P = Q + iU. The wavelets are additionally directional (non-axisymmetric). This allows different morphologies of signals to be separated and therefore the cleaning algorithm is localised using an additional domain of information. The advantage of spin wavelets over standard scalar wavelets is to simultaneously and self-consistently probe scales and directions in the polarisation signal P = Q + iU and in the underlying E and B modes, therefore providing the ability to perform component separation and E-B decomposition concurrently for the first time. We test Spin-SILC on full-mission Planck simulations and data and show the capacity to correctly recover the underlying cosmological E and B modes. We also demonstrate a strong consistency of our CMB maps with those derived from existing component separation methods. Spin-SILC can be combined with the pseudo- and pure E-B spin wavelet estimators presented in a companion paper to reliably extract the cosmological signal in the presence of complicated sky cuts and noise. Therefore, it will provide a computationally-efficient method to accurately extract the CMB E and B modes for future polarisation experiments.

  17. Spin voltage generation across rare earth spin filter barriers

    NASA Astrophysics Data System (ADS)

    Miao, Guoxing; Chang, Joonyeon; Moodera, Jagadeesh

    2011-03-01

    When a metal is in close contact with a rare-earth based magnetic compound, strong exchange interaction exists between the localized 4f electrons and the free moving conduction electrons. One important consequence is that the spin degeneracy among the conduction electrons is lifted, showing up as an effective Zeeman splitting higher than tens of Tesla in low dimensional systems such as graphene and other 2DEG. We perform our work using a vertical transport geometry, which consists of double spin filtering barriers based on a ferromagnetic Eu chalcogenide - EuS. A thin Al metallic layer is sandwiched in the middle and its conduction electrons thus experience the strong spin splitting, which is subsequently detected via the spin filtering effect. A spontaneous spin dependent voltage appears across such a device, and its polarity is directly determined by the EuS/Al interface. The voltage level difference between the spin-parallel and -antiparallel configurations is as large as a few mV. Such spin splitting also induces a clear universal behavior in the observed TMR bias dependence. Such spin voltage effect offers a possibility of directly converting magnetic exchange energy into electrical power. This work is supported by NSF DMR 0504158, ONR N00014-06-1-0235, and KIST-MIT project funds.

  18. Spin pumping and spin-transfer torques in antiferromagnet

    NASA Astrophysics Data System (ADS)

    Niu, Qian

    2015-03-01

    Spin pumping and spin-transfer torques are key elements of coupled dynamics of magnetization and conduction electron spin, which have been widely studied in various ferromagnetic materials. Recent progress in spintronics suggests that a spin current can significantly affects the behavior of an antiferromagnetic material, and the electron motion become adiabatic when the staggered field varies sufficiently slowly. However, pumping from antiferromagnets and its relation to current-induced torques is yet unclear. In a recent study, we have solved this puzzle analytically by calculating how electrons scatter off a normal metal-antiferromagnetic interface. The pumped spin and staggered spin currents are derived in terms of the staggered field, the magnetization, and their rates of change. We find that for both compensated and uncompensated interfaces, spin pumping is of a similar magnitude as in ferromagnets; the direction of spin pumping is controlled by the polarization of the driving microwave. Via the Onsager reciprocity relations, the current-induced torques are also derived, the salient feature of which is illustrated by a terahertz nano-oscillator. In collaboration with Ran Cheng, Jiang Xiao, and A. Brataas.

  19. Tensor spin observables and spin stucture at low Q2

    SciTech Connect

    Slifer, Karl J.

    2015-04-01

    We discuss recent spin structure results from Jefferson Lab, and outline an emerging program to study tensor spin observables using solid deuteron targets. These new experiments open the potential to study hidden color, the tensor nature of short range correlations, and to probe for exotic gluonic states.

  20. Middle Cerebral Artery Calcification

    PubMed Central

    Kao, Hung-Wen; Liou, Michelle; Chung, Hsiao-Wen; Liu, Hua-Shan; Tsai, Ping-Huei; Chiang, Shih-Wei; Chou, Ming-Chung; Peng, Giia-Sheun; Huang, Guo-Shu; Hsu, Hsian-He; Chen, Cheng-Yu

    2015-01-01

    Abstract Calcification of the middle cerebral artery (MCA) is uncommon in the healthy elderly. Whether calcification of the MCA is associated with cerebral ischemic stroke remains undetermined. We intended to investigate the association using Agatston calcium scoring of the MCA. This study retrospectively included 354 subjects with ischemic stroke in the MCA territory and 1518 control subjects who underwent computed tomography (CT) of the brain. We recorded major known risk factors for ischemic stroke, including age, gender, hypertension, diabetes mellitus, smoking, hyperlipidemia, and obesity, along with the MCA calcium burden, measured with the Agatston calcium scoring method. Univariate and modified logistic regression analyses were performed to examine the association between the MCA calcification and ischemic stroke. The univariate analyses showed significant associations of ischemic stroke with age, hypertension, diabetes mellitus, smoking, total MCA Agatston score, and the presence of calcification on both or either side of the MCA. Subjects with the presence of MCA calcification on both or either side of the MCA were 8.46 times (95% confidence interval, 4.93–14.53; P < 0.001) more likely to have a cerebral infarct than subjects without MCA calcification after adjustment for the major known risk factors, including age, hypertension, diabetes mellitus, and smoking. However, a higher degree of MCA calcification reflected by the Agatston score was not associated with higher risk of MCA ischemic stroke after adjustment for the confounding factors and presence of MCA calcification. These results suggest that MCA calcification is associated with ischemic stroke in the MCA territory. Further prospective studies are required to verify the clinical implications of the MCA calcification. PMID:26683969

  1. Retinal artery occlusions in children.

    PubMed

    Dharmasena, Aruna; Wallis, Simon

    2014-01-01

    The purpose of this study is to present a case of RAO in a 13 year old girl with a preceding history of hyperextension of the neck at her hairdressers for a long duration and use of her mobile phone handset resting it against the side of her neck presumably exerting some pressure on carotids during the same time. Materials and methods of this study was reported as case report and review of literature. A 13 year-old girl presented with the left supero-nasal scotoma due to an inferior temporal branch retinal artery occlusion (BRAO). She underwent extensive investigations and no underlying cause was discovered. She gave a history of cervical extension over a long period of time while having the hair coloured twice in the preceding week. She also mentioned that she was using her mobile phone more or less continuously during both these occasions keeping it against her neck. Given the above history it is possible that the pressure on the ipsilateral carotid arteries or the prolong neck extension may have been responsible for the formation of a platelet embolus resulting in the BRAO. In conclusion, although cerebro-vascular accidents due to 'beauty parlor stroke syndrome' (JAMA 269:2085-2086, 1993) have been reported previously it has not been reported in children to our knowledge. On the other hand, 'beauty parlor stroke syndrome' occurs due to a dissection of the vertebral arteries or due to mechanical compression of the vertebral arteries during the prolonged hyperextension of the neck. The central retinal artery originates from the internal carotid circulation and it is highly unlikely for an embolus to enter the retinal circulation from the vertebral arteries. Therefore, the authors favour the possibility that the compulsive use of a mobile phone exerting pressure on the carotid arteries for a long time may have led to the formation of an embolus and subsequent RAO in this case.

  2. Unconventional spin texture in a noncentrosymmetric quantum spin Hall insulator

    NASA Astrophysics Data System (ADS)

    Mera Acosta, C.; Babilonia, O.; Abdalla, L.; Fazzio, A.

    2016-07-01

    We propose that the simultaneous presence of both Rashba and band inversion can lead to a Rashba-like spin splitting formed by two bands with the same in-plane helical spin texture. Because of this unconventional spin texture, the backscattering is forbidden in edge and bulk conductivity channels. We propose a noncentrosymmetric honeycomb-lattice quantum spin Hall (QSH) insulator family formed by the IV, V, and VII elements with this property. The system formed by Bi, Pb, and I atoms is mechanically stable and has both a large Rashba spin splitting of 60 meV and a large nontrivial band gap of 0.14 eV. Since the edge and the bulk states are protected by the time-reversal (TR) symmetry, contrary to what happens in most doped QSH insulators, the bulk states do not contribute to the backscattering in the electronic transport, allowing the construction of a spintronic device with less energy loss.

  3. Spin slush in an extended spin ice model

    PubMed Central

    Rau, Jeffrey G.; Gingras, Michel J. P.

    2016-01-01

    We present a new classical spin liquid on the pyrochlore lattice by extending spin ice with further neighbour interactions. We find that this disorder-free spin model exhibits a form of dynamical heterogeneity with extremely slow relaxation for some spins, while others fluctuate quickly down to zero temperature. We thus call this state spin slush, in analogy to the heterogeneous mixture of solid and liquid water. This behaviour is driven by the structure of the ground-state manifold which extends the celebrated two-in/two-out ice states to include branching structures built from three-in/one-out, three-out/one-in and all-in/all-out tetrahedra defects. Distinctive liquid-like patterns in the magnetic correlations serve as a signature of this intermediate range order. Possible applications to materials as well the effects of quantum tunnelling are discussed. PMID:27470199

  4. Spin slush in an extended spin ice model.

    PubMed

    Rau, Jeffrey G; Gingras, Michel J P

    2016-01-01

    We present a new classical spin liquid on the pyrochlore lattice by extending spin ice with further neighbour interactions. We find that this disorder-free spin model exhibits a form of dynamical heterogeneity with extremely slow relaxation for some spins, while others fluctuate quickly down to zero temperature. We thus call this state spin slush, in analogy to the heterogeneous mixture of solid and liquid water. This behaviour is driven by the structure of the ground-state manifold which extends the celebrated two-in/two-out ice states to include branching structures built from three-in/one-out, three-out/one-in and all-in/all-out tetrahedra defects. Distinctive liquid-like patterns in the magnetic correlations serve as a signature of this intermediate range order. Possible applications to materials as well the effects of quantum tunnelling are discussed. PMID:27470199

  5. Spin slush in an extended spin ice model

    NASA Astrophysics Data System (ADS)

    Rau, Jeffrey G.; Gingras, Michel J. P.

    2016-07-01

    We present a new classical spin liquid on the pyrochlore lattice by extending spin ice with further neighbour interactions. We find that this disorder-free spin model exhibits a form of dynamical heterogeneity with extremely slow relaxation for some spins, while others fluctuate quickly down to zero temperature. We thus call this state spin slush, in analogy to the heterogeneous mixture of solid and liquid water. This behaviour is driven by the structure of the ground-state manifold which extends the celebrated two-in/two-out ice states to include branching structures built from three-in/one-out, three-out/one-in and all-in/all-out tetrahedra defects. Distinctive liquid-like patterns in the magnetic correlations serve as a signature of this intermediate range order. Possible applications to materials as well the effects of quantum tunnelling are discussed.

  6. Spin injection and spin transport in paramagnetic insulators

    DOE PAGES

    Okamoto, Satoshi

    2016-02-22

    We investigate the spin injection and the spin transport in paramagnetic insulators described by simple Heisenberg interactions using auxiliary particle methods. Some of these methods allow access to both paramagnetic states above magnetic transition temperatures and magnetic states at low temperatures. It is predicted that the spin injection at an interface with a normal metal is rather insensitive to temperatures above the magnetic transition temperature. On the other hand below the transition temperature, it decreases monotonically and disappears at zero temperature. We also analyze the bulk spin conductance. We show that the conductance becomes zero at zero temperature as predictedmore » by linear spin wave theory but increases with temperature and is maximized around the magnetic transition temperature. These findings suggest that the compromise between the two effects determines the optimal temperature for spintronics applications utilizing magnetic insulators.« less

  7. Intrinsic spin torque without spin-orbit coupling

    PubMed Central

    Kim, Kyoung-Whan; Lee, Kyung-Jin; Lee, Hyun-Woo; Stiles, M. D.

    2016-01-01

    We derive an intrinsic contribution to the non-adiabatic spin torque for non-uniform magnetic textures. It differs from previously considered contributions in several ways and can be the dominant contribution in some models. It does not depend on the change in occupation of the electron states due to the current flow but rather is due to the perturbation of the electronic states when an electric field is applied. Therefore it should be viewed as electric-field-induced rather than current-induced. Unlike previously reported non-adiabatic spin torques, it does not originate from extrinsic relaxation mechanisms nor spin-orbit coupling. This intrinsic non-adiabatic spin torque is related by a chiral connection to the intrinsic spin-orbit torque that has been calculated from the Berry phase for Rashba systems. PMID:26877628

  8. Magnetar Spin-Down.

    PubMed

    Harding; Contopoulos; Kazanas

    1999-11-10

    We examine the effects of a relativistic wind on the spin-down of a neutron star and apply our results to the study of soft gamma repeaters (SGRs), which are thought to be neutron stars with magnetic fields greater than 1014 G. We derive a spin-down formula that includes torques from both dipole radiation and episodic or continuous particle winds. We find that if SGR 1806-20 puts out a continuous particle wind of 1037 ergs s-1, then the pulsar age is consistent with that of the supernova remnant, but the derived surface dipole magnetic field is only 3x1013 G, in the range of normal radio pulsars. If instead the particle wind flows are episodic with small duty cycle, then the observed period derivatives imply magnetar-strength fields, while still allowing characteristic ages within a factor of 2 of the estimated supernova remnant age. Close monitoring of the periods of SGRs will allow us to establish or place limits on the wind duty cycle and thus the magnetic field and age of the neutron star.

  9. SAMPEX Spin Stabilized Mode

    NASA Technical Reports Server (NTRS)

    Tsai, Dean C.; Markley, F. Landis; Watson, Todd P.

    2008-01-01

    The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), the first of the Small Explorer series of spacecraft, was launched on July 3, 1992 into an 82' inclination orbit with an apogee of 670 km and a perigee of 520 km and a mission lifetime goal of 3 years. After more than 15 years of continuous operation, the reaction wheel began to fail on August 18,2007. With a set of three magnetic torquer bars being the only remaining attitude actuator, the SAMPEX recovery team decided to deviate from its original attitude control system design and put the spacecraft into a spin stabilized mode. The necessary operations had not been used for many years, which posed a challenge. However, on September 25, 2007, the spacecraft was successfully spun up to 1.0 rpm about its pitch axis, which points at the sun. This paper describes the diagnosis of the anomaly, the analysis of flight data, the simulation of the spacecraft dynamics, and the procedures used to recover the spacecraft to spin stabilized mode.

  10. Repair of Internal Iliac Artery Aneurysm Anastomosed to Donor Renal Artery in a Renal Transplant Patient

    PubMed Central

    Takano, Hiroshi; Kin, Keiwa; Maeda, Shuusaku

    2016-01-01

    We herein report a successful repair of an internal iliac artery aneurysm in a renal transplant patient. At renal transplantation, the main renal artery and accessory renal artery had been anastomosed to the right internal iliac artery and right external iliac artery, respectively. The patient underwent resection and graft replacement of the iliac artery aneurysm with reattachment of the main renal artery to the right external iliac artery through a midline laparotomy with repeated topical cold perfusion for renal protection. The postoperative course was uneventful, and no evidence of renal function impairment was present at discharge. PMID:27738467

  11. Histopathologic Characteristics of a Coronary-pulmonary Artery Fistula with a Coronary Artery Aneurysm

    PubMed Central

    Sakata, Noriyuki; Minematsu, Noritoshi; Morishige, Noritsugu; Tashiro, Tadashi; Imanaga, Yoshinobu

    2011-01-01

    Here, we report a case of a 59-year-old woman with a coronary-pulmonary artery fistula with a concomitant coronary artery aneurysm, which comprised an anomalous coronary artery originating at the right coronary cusp, an aberrant branch of the left anterior descending artery, and a coronary artery aneurysm draining into the main pulmonary artery. Histopathologically, non-dilated anomalous coronary artery showed the preservation of internal elastic lamina and medial smooth muscle cell phenotype which lacked in the aneurysmal wall. Thus, the disrupted internal elastic lamina and phenotypic change of medial smooth muscle cells might contribute to aneurysm formation in a coronary-pulmonary arterial fistula. PMID:23555427

  12. Spin-noise correlations and spin-noise exchange driven by low-field spin-exchange collisions

    NASA Astrophysics Data System (ADS)

    Dellis, A. T.; Loulakis, M.; Kominis, I. K.

    2014-09-01

    The physics of spin-exchange collisions have fueled several discoveries in fundamental physics and numerous applications in medical imaging and nuclear magnetic resonance. We report on the experimental observation and theoretical justification of spin-noise exchange, the transfer of spin noise from one atomic species to another. The signature of spin-noise exchange is an increase of the total spin-noise power at low magnetic fields, on the order of 1 mG, where the two-species spin-noise resonances overlap. The underlying physical mechanism is the two-species spin-noise correlation induced by spin-exchange collisions.

  13. Enhanced spin polarization in graphene with spin energy gap induced by spin-orbit coupling and strain

    SciTech Connect

    Liu, Zheng-Fang; Wu, Qing-Ping E-mail: aixichen@ecjtu.jx.cn; Chen, Ai-Xi E-mail: aixichen@ecjtu.jx.cn; Xiao, Xian-Bo; Liu, Nian-Hua

    2014-05-28

    We investigate the possibility of spin polarization in graphene. The result shows that a spin energy gap can be opened in the presence of both spin-orbit coupling and strain. We find that high spin polarization with large spin-polarized current is achieved in the spin energy gap. However, only one of the two modulations is present, no spin polarization can be generated. So the combination of the two modulations provides a way to design tunable spin polarization without need for a magnetic element or an external magnetic field.

  14. Spin transport in p-type germanium.

    PubMed

    Rortais, F; Oyarzún, S; Bottegoni, F; Rojas-Sánchez, J-C; Laczkowski, P; Ferrari, A; Vergnaud, C; Ducruet, C; Beigné, C; Reyren, N; Marty, A; Attané, J-P; Vila, L; Gambarelli, S; Widiez, J; Ciccacci, F; Jaffrès, H; George, J-M; Jamet, M

    2016-04-27

    We report on the spin transport properties in p-doped germanium (Ge-p) using low temperature magnetoresistance measurements, electrical spin injection from a ferromagnetic metal and the spin pumping-inverse spin Hall effect method. Electrical spin injection is carried out using three-terminal measurements and the Hanle effect. In the 2-20 K temperature range, weak antilocalization and the Hanle effect provide the same spin lifetime in the germanium valence band (≈1 ps) in agreement with predicted values and previous optical measurements. These results, combined with dynamical spin injection by spin pumping and the inverse spin Hall effect, demonstrate successful spin accumulation in Ge. We also estimate the spin Hall angle θ(SHE) in Ge-p (6-7 x 10(-4) at room temperature, pointing out the essential role of ionized impurities in spin dependent scattering.

  15. Spin transport in p-type germanium

    NASA Astrophysics Data System (ADS)

    Rortais, F.; Oyarzún, S.; Bottegoni, F.; Rojas-Sánchez, J.-C.; Laczkowski, P.; Ferrari, A.; Vergnaud, C.; Ducruet, C.; Beigné, C.; Reyren, N.; Marty, A.; Attané, J.-P.; Vila, L.; Gambarelli, S.; Widiez, J.; Ciccacci, F.; Jaffrès, H.; George, J.-M.; Jamet, M.

    2016-04-01

    We report on the spin transport properties in p-doped germanium (Ge-p) using low temperature magnetoresistance measurements, electrical spin injection from a ferromagnetic metal and the spin pumping-inverse spin Hall effect method. Electrical spin injection is carried out using three-terminal measurements and the Hanle effect. In the 2-20 K temperature range, weak antilocalization and the Hanle effect provide the same spin lifetime in the germanium valence band (≈1 ps) in agreement with predicted values and previous optical measurements. These results, combined with dynamical spin injection by spin pumping and the inverse spin Hall effect, demonstrate successful spin accumulation in Ge. We also estimate the spin Hall angle {θ\\text{SHE}} in Ge-p (6-7× {{10}-4} ) at room temperature, pointing out the essential role of ionized impurities in spin dependent scattering.

  16. Spin Technologies in Silicon Carbide

    NASA Astrophysics Data System (ADS)

    Klimov, Paul

    2015-03-01

    Over the past several decades SiC has evolved from being a simple abrasive to a versatile material platform for high-power electronics, optoelectronics, and nanomechanical devices. These technologies have been driven by advanced growth, doping, and processing capabilities, and the ready availability of large-area, single-crystal SiC wafers. Recent advances have also established SiC as a promising host for a novel class of technologies based on the spin of intrinsic color centers. In particular, the divacancies and related defects have ground-state electronic-spin triplets with ms-long coherence times that can be optically addressed near telecom wavelengths and manipulated with magnetic, electric, and strain fields. Recently, divacancy addressability has been extended to the single defect level, laying foundation for single spin technologies in SiC. This rapidly developing field has prompted research into the SiC material host to understand how defect-bound electron spins interact with their surrounding nuclear spin bath. Although nuclear spins are typically a major source of decoherence in color-center spin systems, they are also an important resource since they interact with magnetic fields orders of magnitude more weakly than electronic spins. This fact has motivated their use for quantum memories and ultra-sensitive sensors. In this talk I will review advances in this rapidly developing field and discuss our efforts towards this latter goal. This work was supported by the AFOSR, DARPA, and the NSF.

  17. Invariant Spin in the Proton

    SciTech Connect

    Thomas, Anthony

    2008-11-01

    We discuss recent theoretical progress in understanding the distribution of spin and orbital angular momentum in the proton. Particular attention is devoted to the effect of QCD evolution and to the distinction between "chiral" and "invariant" spin. This is particularly significant with respect to the possible presence of polarized strange quarks.

  18. Microfabricated Spin Polarized Atomic Magnetometers

    NASA Astrophysics Data System (ADS)

    Jimenez Martinez, Ricardo

    Spin polarized atomic magnetometers involve the preparation of atomic spins and their detection for monitoring magnetic fields. Due to the fact that magnetic fields are ubiquitous in our world, spin polarized atomic magnetometers are used in a wide range of applications from the detection of magnetic fields generated by the human heart and brain to the detection of nuclear magnetic resonance. In this thesis we developed microfabricated spin polarized atomic magnetometers. These sensors are based on optical pumping and spin-exchange collisions between alkali atoms and noble gases contained in microfabricated millimeter-scale vapor cells. In the first part of the thesis, we improved different features of current microfabricated optical magnetometers. Specifically, we improved the bandwidth of these devices, without degrading their magnetic field sensitivity, by broadening their magnetic resonance through spin-exchange collisions between alkali atoms. We also implemented all-optical excitation techniques to avoid problems, such as the magnetic perturbation of the environment, induced by the radio-frequency fields used in some of these sensors. In the second part of the thesis we demonstrated a microfluidic chip for the optical production and detection of hyperpolarized Xe gas through spin-exchange collisions with optically pumped Rb atoms. These devices are critical for the widespread use of spin polarized atomic magnetometers in applications requiring simple, compact, low-cost, and portable instrumentation.

  19. Invariant Spin in the Proton

    SciTech Connect

    Thomas, Anthony W.

    2008-10-13

    We discuss recent theoretical progress in understanding the distribution of spin and orbital angular momentum in the proton. Particular attention is devoted to the effect of QCD evolution and to the distinction between 'chiral' and 'invariant' spin. This is particularly significant with respect to the possible presence of polarized strange quarks.

  20. Engineering of arteries in vitro.

    PubMed

    Huang, Angela H; Niklason, Laura E

    2014-06-01

    This review will focus on two elements that are essential for functional arterial regeneration in vitro: the mechanical environment and the bioreactors used for tissue growth. The importance of the mechanical environment to embryological development, vascular functionality, and vascular graft regeneration will be discussed. Bioreactors generate mechanical stimuli to simulate biomechanical environment of arterial system. This system has been used to reconstruct arterial grafts with appropriate mechanical strength for implantation by controlling the chemical and mechanical environments in which the grafts are grown. Bioreactors are powerful tools to study the effect of mechanical stimuli on extracellular matrix architecture and mechanical properties of engineered vessels. Hence, biomimetic systems enable us to optimize chemo-biomechanical culture conditions to regenerate engineered vessels with physiological properties similar to those of native arteries. In addition, this article reviews various bioreactors designed especially to apply axial loading to engineered arteries. This review will also introduce and examine different approaches and techniques that have been used to engineer biologically based vascular grafts, including collagen-based grafts, fibrin-gel grafts, cell sheet engineering, biodegradable polymers, and decellularization of native vessels.

  1. Posterior cerebral artery territory infarctions.

    PubMed

    Cereda, Carlo; Carrera, Emmanuel

    2012-01-01

    Infarctions in the territory of the posterior cerebral artery (PCA) occur in about 5-10% of all ischemic strokes. The PCA can be divided into 'deep' (P1 and P2 segments) and 'superficial' (P3 and P4) segments. Occlusion of paramedian perforating arteries arising from P1 causes rostral midbrain infarction with or without thalamic lesion. The classical clinical triad after thalamomesencephalic infarcts is hypersomnolence, cognitive deficits and vertical oculomotor paresis. Two main arterial groups arise from P2: infarction in the territory of the thalamogeniculate arteries causes severe contralateral hypesthesia and ataxia, whereas infarction in the territory of the posterior choroidal arteries results in sectoranopia with involvement of the lateral geniculate body. After superficial PCA infarcts, visual field defects and somatosensory deficits are the most frequent signs. Additionally, disorders of reading may be seen after unilateral left infarction and disorientation for place and visual neglect after right lesion. After bilateral PCA infarcts, amnesia, cortical blindness (the patient cannot see but pretend he can) may occur. Acute thrombolysis is as useful after PCA infarctions as after anterior circulation strokes. Mortality after PCA strokes is low, but long-term behavioral and cognitive deficits are underestimated.

  2. Photo-spin-voltaic effect

    NASA Astrophysics Data System (ADS)

    Ellsworth, David; Lu, Lei; Lan, Jin; Chang, Houchen; Li, Peng; Wang, Zhe; Hu, Jun; Johnson, Bryan; Bian, Yuqi; Xiao, Jiang; Wu, Ruqian; Wu, Mingzhong

    2016-09-01

    The photo-voltaic effect typically occurs in semiconductors and involves photon-driven excitation of electrons from a valence band to a conduction band. In a region such as a p-n junction that has a built-in electric field, the excited electrons and holes diffuse in opposite directions, resulting in an electric voltage. This letter reports that a spin voltage can be created by photons in a non-magnetic metal that is in close proximity to a magnetic insulator: a photo-spin-voltaic effect. The experiments use platinum/magnetic insulator bilayer structures. On exposure to light, there occurs photon-driven, spin-dependent excitation of electrons in several platinum atomic layers near the platinum/magnetic insulator interface. The excited electrons and holes diffuse in different manners, and this gives rise to an effective spin voltage at the interface and a corresponding pure spin current that flows across the platinum.

  3. First jejunal artery, an alternative graft for right hepatic artery reconstruction.

    PubMed

    Aryal, Bibek; Komokata, Teruo; Kadono, Jun; Motodaka, Hiroyuki; Ueno, Tetsuya; Furoi, Akira; Imoto, Yutaka

    2015-04-01

    Common bile duct cancer invading right hepatic artery is sometimes diagnosed intraoperatively. Excision and safe reconstruction of the artery with suitable graft is essential. Arterial reconstruction with autologous saphenous vein graft is the preferred method practiced routinely. However the right hepatic artery reconstruction has also been carried out with several other vessels like gastroduodenal artery, right gastroepiploic artery or the splenic artery. We report a case of 63-year-old man presenting with history of progressive jaundice, pruritus and impaired appetite. Following various imaging modalities including computed tomography, endoscopic retrograde cholangiopancreatography, magnetic resonance cholangiopancreatography, intraductal ultrasound extrahepatic bile duct cancer was diagnosed; however, none of those detected vessel invasion. Intraoperatively, right hepatic artery invasion was revealed. Right hepatic artery was resected and reconstructed with a graft harvested from the first jejunal artery (JA). Postoperative outcome was satisfactory with a long-term graft patency. First JA can be a reliable graft option for right hepatic artery reconstruction.

  4. Distinguishing spin relaxation mechanisms in organic semiconductors.

    PubMed

    Harmon, N J; Flatté, M E

    2013-04-26

    A theory is introduced for spin relaxation and spin diffusion of hopping carriers in a disordered system. For disorder described by a distribution of waiting times between hops (e.g., from multiple traps, site-energy disorder, and/or positional disorder) the dominant spin relaxation mechanisms in organic semiconductors (hyperfine, hopping-induced spin-orbit, and intrasite spin relaxation) each produce different characteristic spin relaxation and spin diffusion dependences on temperature. The resulting unique experimental signatures predicted by the theory for each mechanism in organic semiconductors provide a prescription for determining the dominant spin relaxation mechanism. PMID:23679752

  5. Theory of the spin Seebeck effect.

    PubMed

    Adachi, Hiroto; Uchida, Ken-ichi; Saitoh, Eiji; Maekawa, Sadamichi

    2013-03-01

    The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental efforts have shown that the magnon and phonon degrees of freedom play crucial roles in the spin Seebeck effect. In this paper, we present the theoretical basis for understanding the spin Seebeck effect and briefly discuss other thermal spin effects.

  6. Extrinsic spin Hall effects measured with lateral spin valve structures

    NASA Astrophysics Data System (ADS)

    Niimi, Y.; Suzuki, H.; Kawanishi, Y.; Omori, Y.; Valet, T.; Fert, A.; Otani, Y.

    2014-02-01

    The spin Hall effect (SHE), induced by spin-orbit interaction in nonmagnetic materials, is one of the promising phenomena for conversion between charge and spin currents in spintronic devices. The spin Hall (SH) angle is the characteristic parameter of this conversion. We have performed experiments of the conversion from spin into charge currents by the SHE in lateral spin valve structures. We present experimental results on the extrinsic SHEs induced by doping nonmagnetic metals, Cu or Ag, with impurities having a large spin-orbit coupling, Bi or Pb, as well as results on the intrinsic SHE of Au. The SH angle induced by Bi in Cu or Ag is negative and particularly large for Bi in Cu, 10 times larger than the intrinsic SH angle in Au. We also observed a large SH angle for CuPb, but the SHE signal disappeared in a few days. Such an aging effect could be related to a fast mobility of Pb in Cu and has not been observed in CuBi alloys.

  7. ACUTE RETINAL ARTERIAL OCCLUSIVE DISORDERS

    PubMed Central

    Hayreh, Sohan Singh

    2011-01-01

    The initial section deals with basic sciences; among the various topics briefly discussed are the anatomical features of ophthalmic, central retinal and cilioretinal arteries which may play a role in acute retinal arterial ischemic disorders. Crucial information required in the management of central retinal artery occlusion (CRAO) is the length of time the retina can survive following that. An experimental study shows that CRAO for 97 minutes produces no detectable permanent retinal damage but there is a progressive ischemic damage thereafter, and by 4 hours the retina has suffered irreversible damage. In the clinical section, I discuss at length various controversies on acute retinal arterial ischemic disorders. Classification of acute retinal arterial ischemic disorders These are of 4 types: CRAO, branch retinal artery occlusion (BRAO), cotton wools spots and amaurosis fugax. Both CRAO and BRAO further comprise multiple clinical entities. Contrary to the universal belief, pathogenetically, clinically and for management, CRAO is not one clinical entity but 4 distinct clinical entities – non-arteritic CRAO, non-arteritic CRAO with cilioretinal artery sparing, arteritic CRAO associated with giant cell arteritis (GCA) and transient non-arteritic CRAO. Similarly, BRAO comprises permanent BRAO, transient BRAO and cilioretinal artery occlusion (CLRAO), and the latter further consists of 3 distinct clinical entities - non-arteritic CLRAO alone, non-arteritic CLRAO associated with central retinal vein occlusion and arteritic CLRAO associated with GCA. Understanding these classifications is essential to comprehend fully various aspects of these disorders. Central retinal artery occlusion The pathogeneses, clinical features and management of the various types of CRAO are discussed in detail. Contrary to the prevalent belief, spontaneous improvement in both visual acuity and visual fields does occur, mainly during the first 7 days. The incidence of spontaneous visual

  8. [Trapped popliteal vein and artery].

    PubMed

    Allal, J; Gallimard, J F; Goubbault, F; Lelong, J; Barbier, J; Barraine, R

    1986-03-01

    A report is made of 3 observations of vascular constrictions in the knee hollow of three young adults: two constrictions of the popliteal artery, one by abnormal insertion of a tendon of the gastrocnemius muscle and of the arterial passage, the other by a fibrous band surrounding the artery. In one observation, the disorder was revealed by acute ischemia of one limb. The third observation was of a sural phlebitis with secondary repetition at the constriction of the popliteal vein by Soleaire's arcade. In all cases examination using the Doppler effect, in baseline and especially dynamic position, gives a diagnosis and allows postoperative monitoring. Bilateral arteriography, both static and dynamic, allows a precise diagnosis to be given and reveals the extent of vascular lesions, which conditions the operative technique. Treatment is always surgical, with exploration of the contralateral side if a constriction is suspected, even if it is asymptomatic. PMID:3707018

  9. Spontaneous internal carotid artery dissection.

    PubMed

    Khimenko, L P; Esham, H R; Ahmed, W

    2000-10-01

    Once considered uncommon, spontaneous dissection of the carotid artery is an increasingly recognized cause of stroke, headache, cranial nerve palsy, or ophthalmologic events, especially in young adults. Even in the presence of existing signs and symptoms, the diagnosis can be missed by experienced physicians of all specialties. We report a case of spontaneous internal carotid artery dissection in a 38-year-old woman with a cortical stroke and visual disturbances as initial symptoms. The diagnosis was confirmed by magnetic resonance imaging/angiography and by angiography. Prompt anticoagulation was instituted, and the patient had complete resolution of symptoms. Cervicocephalic arterial dissection should be included in the differential diagnosis of the causes of cerebrovascular events.

  10. Spin Orbit Interaction Engineering for beyond Spin Transfer Torque memory

    NASA Astrophysics Data System (ADS)

    Wang, Kang L.

    Spin transfer torque memory uses electron current to transfer the spin torque of electrons to switch a magnetic free layer. This talk will address an alternative approach to energy efficient non-volatile spintronics through engineering of spin orbit interaction (SOC) and the use of spin orbit torque (SOT) by the use of electric field to improve further the energy efficiency of switching. I will first discuss the engineering of interface SOC, which results in the electric field control of magnetic moment or magneto-electric (ME) effect. Magnetic memory bits based on this ME effect, referred to as magnetoelectric RAM (MeRAM), is shown to have orders of magnitude lower energy dissipation compared with spin transfer torque memory (STTRAM). Likewise, interests in spin Hall as a result of SOC have led to many advances. Recent demonstrations of magnetization switching induced by in-plane current in heavy metal/ferromagnetic heterostructures have been shown to arise from the large SOC. The large SOC is also shown to give rise to the large SOT. Due to the presence of an intrinsic extraordinarily strong SOC and spin-momentum lock, topological insulators (TIs) are expected to be promising candidates for exploring spin-orbit torque (SOT)-related physics. In particular, we will show the magnetization switching in a chromium-doped magnetic TI bilayer heterostructure by charge current. A giant SOT of more than three orders of magnitude larger than those reported in heavy metals is also obtained. This large SOT is shown to come from the spin-momentum locked surface states of TI, which may further lead to innovative low power applications. I will also describe other related physics of SOC at the interface of anti-ferromagnetism/ferromagnetic structure and show the control exchange bias by electric field for high speed memory switching. The work was in part supported by ERFC-SHINES, NSF, ARO, TANMS, and FAME.

  11. Spin Splitting and Spin Current in Strained Bulk Semiconductors

    SciTech Connect

    Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-01-15

    We present a theory for two recent experiments in bulk strained semiconductors and show that a new, previously overlooked, strain spin-orbit coupling term may play a fundamental role. We propose simple experiments that could clarify the origin of strain-induced spin-orbit coupling terms in inversion asymmetric semiconductors. We predict that a uniform magnetization parallel to the electric field will be induced in the samples studied in for specific directions of the applied electric field. We also propose special geometries to detect spin currents in strained semiconductors.

  12. The kidney and arterial hypertension.

    PubMed

    Ruilope, L M; Campo, C; Lahera, V

    1993-01-01

    It has been known for some time that a relationship exists between the kidney and blood pressure. The renal origin of arterial hypertension has been demonstrated in different animal models resembling human hypertension, with data from humans seeming to confirm this hypothesis. On the other hand, the renal vasculature also suffers the consequences of arterial hypertension, and renal insufficiency can develop as a result of elevated blood pressure levels. Antihypertensive therapy can prevent the development of renal damage secondary to hypertension. For example, calcium antagonists possess specific renal effects that not only facilitate their antihypertensive capacity but also protect the kidney from the development of renal failure.

  13. Flows In Model Human Femoral Arteries

    NASA Technical Reports Server (NTRS)

    Back, Lloyd H.; Kwack, Eug Y.; Crawford, Donald W.

    1990-01-01

    Flow is visualized with dye traces, and pressure measurements made. Report describes experimental study of flow in models of human femoral artery. Conducted to examine effect of slight curvature of artery on flow paths and distribution of pressure.

  14. Angioplasty and stent placement - carotid artery

    MedlinePlus

    Carotid angioplasty and stenting; CAS; Angioplasty - carotid artery; Carotid artery stenosis - angioplasty; ... Carotid angioplasty and stenting (CAS) is done using a small surgical cut. Your surgeon will make a surgical cut ...

  15. Facts about Transposition of the Great Arteries

    MedlinePlus

    ... Septal Defect Atrioventricular Septal Defect Coarctation of the Aorta D-Transposition of the Great Arteries Hypoplastic Left ... of the heart—the pulmonary artery and the aorta —are switched in position, or “transposed”. Normally, blood ...

  16. Transposition of the Greater Arteries (TGA)

    MedlinePlus

    ... Heart Disease Diseases of the arteries, valves, and aorta, as well as cardiac rhythm disturbances Aortic Valve ... Transposition of the Great Arteries Coarctation of the Aorta Truncus Arteriosus Single Ventricle Defects Lung, Esophageal, and ...

  17. Tailoring the flow sensitivity of fast spin-echo sequences for noncontrast peripheral MR angiography

    PubMed Central

    Storey, Pippa; Atanasova, Iliyana P.; Lim, Ruth P.; Xu, Jian; Kim, Daniel; Chen, Qun; Lee, Vivian S.

    2011-01-01

    There has recently been renewed interest in non-contrast techniques for peripheral MR angiography following the discovery of an association between gadolinium-based contrast agents and nephrogenic systemic fibrosis (NSF) in patients with renal insufficiency. The ‘fresh blood imaging’ technique proposed by Miyazaki et al. involves the subtraction of two 3D fast spin-echo image sets, one acquired in systole, when the arteries appear dark due to flow-related dephasing, and the other obtained in diastole, when the arteries are brighter. Our goal was to investigate how parameters of the fast spin-echo sequence influence its flow sensitivity, and how that in turn impacts the depiction of large and small arteries. Results from phantom experiments and human studies in the calf suggest that the flow sensitivity is governed largely by the flip angle of the radiofrequency refocusing pulses. The area of the spoiler gradients has a lesser effect, and at low flip angles the echo time plays a role. These parameters can be optimized to obtain good depiction of the calf arteries in healthy subjects. It remains to be seen whether they provide sufficient control over flow sensitivity to achieve diagnostic-quality images in other vascular beds and in the presence of pathology. PMID:20725934

  18. Relativistic Definition of Spin Operators

    NASA Astrophysics Data System (ADS)

    Ryder, Lewis H.

    2002-12-01

    Some years ago Mashhoon [1] made the highly interesting suggestion that there existed a coupling of spin with rotations, just as there exists such a coupling with orbital angular momentum, as seen in the Sagnac effect, for example. Spin being essentially a quantum phenomenon, the obvious place to look for this was by studying the Dirac equation, and Hehl and Ni, in such an investigation [2], indeed found a coupling term of just the type Mashhoon had envisaged. Part of their procedure, however, was to take the nonrelativistic limit, and this was done by performing appropriate Foldy-Wouthuysen (FW) transformations. In the nonrelativistic limit, it is well-known that the spin operators for Dirac particles are in essence the Pauli matrices; but it is also well-known, and indeed was part of the motivation for Foldy and Wouthuysen's paper, that for fully-fledged Dirac particles the (4×4 generalisation of the) Pauli matrices do not yield satisfactory spin operators, since spin defined in this way would not be conserved. The question therefore presented itself: is there a relativistic spin operator for Dirac particles, such that in the relativistic, as well as the nonrelativistic, régime a Mashhoon spin-rotation coupling exists?...

  19. Taming spin decoherence in silicon

    NASA Astrophysics Data System (ADS)

    Lyon, Stephen

    2013-03-01

    Electron spins in semiconductor hosts have been candidate qubits since the early days of experimental quantum computing research, but it was generally assumed that the solid state environment would limit coherence to times much shorter than that seen in isolated atoms or ions. The longest measured electron spin coherence, measured in isotopically enriched silicon, was of order 1 ms. However, over the last 8 or 10 years the measured electron spin coherence times have steadily increased as materials and experimental techniques have improved. Much of the decoherence observed in the early ensemble Electron Spin Resonance (ESR) experiments arose from interactions amongst the spins being measured. In the most highly enriched bulk silicon measured to date, the residual silicon isotopes with nuclear magnetic moments affect the coherence of electrons bound to phosphorus donors on about a 1 second time scale. The remaining decoherence is still dominated by interactions between the donor spins, even in very lightly doped Si. Other decoherence processes have been shown to be at least an order of magnitude weaker. Recent work suggested that longer spin coherence would be obtained in bismuth doped Si, where magnetic-field insensitive ``clock transitions'' occur in the GHz frequency range. Recent experiments are bearing out these suggestions. This work was supported in part by the ARO and NSF.

  20. Turbulent Flow Past Spinning Cylinders

    NASA Astrophysics Data System (ADS)

    Mehmedagic, Igbal; Carlucci, Donald; Carlucci, Pasquale; Thangam, Siva

    2009-11-01

    Flow past cylinders aligned along their axis where a base freely spins while attached to a non-spinning forebody is considered from a computational and experimental point of view. The time-averaged equations of motion and energy are solved using the modeled form of transport equations for the turbulence kinetic energy and the scalar form of turbulence dissipation with an efficient finite-volume algorithm. An anisotropic two-equation Reynolds-stress model that incorporates the effect of rotation-modified energy spectrum and swirl is used to perform computations for the flow past axially rotating cylinders. Both rigid cylinders as well as that of cylinders with free-spinning base are considered from a computational point of view. A subsonic wind tunnel with a forward-sting mounted spinning cylinder is used for experiments. Experiments are performed for a range of spin rates and free stream flow conditions. The experimental results of Carlucci & Thangam (2001) are used to benchmark flow over spinning cylinders. The data is extended to munitions spinning in the wake of other munitions. Applications involving the design of projectiles are discussed.

  1. Spin squeezing, entanglement and correlations

    NASA Astrophysics Data System (ADS)

    Sirsi, Swarnamala

    2004-11-01

    Spin-s assemblies are classified into two mutually exclusive classes: oriented and non-oriented systems. The density matrix rgr, describing oriented systems, can assume diagonal form in the angular momentum basis \\vert sm \\rangle (m=-s \\cdots {+}s ) defined with respect to the axis of quantization, whereas the eigenstates of rgr for the non-oriented assembly cannot all be identified with \\vert sm \\rangle states. A new scheme for constructing a mixed, non-oriented spin-s state using s(2s+1) spinors all pointing in different directions in space and 2s weights is discussed. Such a construction takes its inspiration from Schwinger's idea of realizing an \\vert sm \\rangle state as being made up of (s+m) 'up' spinors and (s-m) 'down' spinors, all defined with respect to a single axis in space. Since the oriented systems are never squeezed, non-oriented spin-1 assemblies which can be prepared in the laboratory with the available NQR technology are examined for signatures of squeezing using our scheme in a frame of reference where the Heisenberg-Robertson uncertainty relation has the same form as the Schrödinger uncertainty relation. It is shown that unlike in the case of the pure spin-1 state where squeezing is synonymous with non-orientedness, a non-oriented spin-1 system need not be squeezed and the existence of entanglement is a necessary but not sufficient condition for the system to be squeezed.

  2. Bilateral Internal Thoracic Artery Configuration for Coronary Artery Bypass Surgery

    PubMed Central

    Boodhwani, Munir; Hanet, Claude; de Kerchove, Laurent; Navarra, Emiliano; Astarci, Parla; Noirhomme, Philippe; El Khoury, Gebrine

    2016-01-01

    Background— Bilateral internal thoracic arteries (BITA) have demonstrated superior patency and improved survival in patients undergoing coronary artery bypass grafting. However, the optimal configuration for BITA utilization and its effect on long-term outcome remains uncertain. Methods and Results— We randomly assigned 304 patients undergoing coronary artery bypass grafting using BITA to either in situ or Y grafting configurations. The primary end point was 3-year angiographic patency. Secondary end points included major adverse cardiac and cerebrovascular events (ie, death from any cause, stroke, myocardial infarction, or repeat revascularization) at 7 years. More coronary targets were able to be revascularized using internal thoracic arteries in patients randomized to Y grafting versus in situ group (3.2±0.8 versus 2.4±0.5 arteries/patient; P<0.01). The primary end point did not show significant differences in graft patency between groups. Secondary end points occurred more frequently in the in situ group (P=0.03), with 7-year rates of 34±10% in the in situ and 25±12% in the Y grafting groups, driven largely by a higher incidence of repeat revascularization in the in situ group (14±4.5% versus 7.4±3.2% at 7 years; P=0.009). There were no significant differences in hospital mortality or morbidity or in late survival, myocardial infarction, or stroke between groups. Conclusions— Three-year systematic angiographic follow-up revealed no significant difference in graft patency between the 2 BITA configurations. However, compared with in situ configuration, the use of BITA in a Y grafting configuration results in lower rates of major adverse cardiovascular and cerebrovascular events at 7 years. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT01666366. PMID:27406988

  3. TRAS principles blight arterial bypass and plasty.

    PubMed

    Kothari, M V; Mehta, L A; Kothari, V M

    1997-01-01

    A new concept--Tissue Requisitions (Principle I)/Relinquishes (Principle II) Arterial Supply--of TRAS principles is introduced to help appreciate the failures/successes of modern medicine's attempts at restoring arterial flow in luminally compromised coronary/carotid fields, an invasive branch rightly called vascular ReRheology, which comprises diagnosing/treating arterial blocks. The technical wizardry of arterial reconstruction (bypass) or lumen--restoration (plasty) has to reckon with the TRAS principles all the time. PMID:10740714

  4. Spin waves in a spin-1 normal Bose gas

    SciTech Connect

    Natu, Stefan S.; Mueller, Erich J.

    2010-05-15

    We present a theory of spin waves in a noncondensed gas of spin-1 bosons and provide both analytic calculations of the linear theory and full numerical simulations of the nonlinear response. We highlight the role of spin-dependent contact interactions in the dynamics of a thermal gas. Although these interactions are small compared to the thermal energy, they set the scale for low-energy, long-wavelength spin waves. In particular, we find that the polar state of {sup 87}Rb is unstable to collisional mixing of magnetic sublevels even in the normal state. We augment our analytic calculations by providing full numerical simulations of a trapped gas, explicitly demonstrating this instability. Further, we show that for strong antiferromagnetic interactions, the polar gas is unstable. Finally, we explore coherent population dynamics in a collisionless transversely polarized gas.

  5. Spin regulation in composite spin-filter barrier devices.

    PubMed

    Miao, Guo-Xing; Chang, Joonyeon; Assaf, Badih A; Heiman, Donald; Moodera, Jagadeesh S

    2014-04-23

    Magnetic insulators are known to provide large effective Zeeman fields that are confined at an interface, making them especially powerful in modifying adjacent one- or two-dimensional electronic structures. Utilizing this phenomenon and the other important property of magnetic insulators--spin filtering--here we report the generation and subsequent detection of a large interface field, as large as tens of tesla in EuS/Al/EuS heterostructures with metallic coulomb islands confined within a magnetic insulator barrier. The unique energy profile across this sandwich structure produces spin-assisted charge transfer across the device, generating a spontaneous spin current and voltage. These unique properties can be practical for controlling spin flows in electronic devices and for energy harvesting.

  6. Enhanced Atomic-Scale Spin Contrast due to Spin Friction

    NASA Astrophysics Data System (ADS)

    Ouazi, S.; Kubetzka, A.; von Bergmann, K.; Wiesendanger, R.

    2014-02-01

    Atom manipulation with the magnetic tip of a scanning tunneling microscope is a versatile technique to construct and investigate well-defined atomic spin arrangements. Here we explore the possibility of using a magnetic adatom as a local probe to image surface spin textures. As a model system we choose a Néel state with 120° between neighboring magnetic moments. Close to the threshold of manipulation, the adatom resides in the threefold, magnetically frustrated hollow sites, and consequently no magnetic signal is detected in manipulation images. At smaller tip-adatom distances, however, the adatom is moved towards the magnetically active bridge sites and due to the exchange force of the tip the manipulation process becomes spin dependent. In this way the adatom can be used as an amplifying probe for the surface spin texture.

  7. Spin scan imaging at Jupiter

    NASA Technical Reports Server (NTRS)

    Sinclair, K. F.

    1973-01-01

    The general feasibility of spin scan imaging from spinning platforms in outer planet orbiters was investigated. The study was limited to consideration of a typical orbiter mission to Jupiter with an orbit designed to provide repetitive close approaches to the Galilean satellites. Discussed are: (1) data requirements for imaging experiments at Jupiter and its satellites; (2) spin scan camera and baseline camera selection; and (3) operational considerations bearing on imager performance. A physical camera model including relationships identifying the supporting requirements was developed and used to determine the characteristics of the baseline camera.

  8. Spinning fluids in general relativity

    NASA Technical Reports Server (NTRS)

    Ray, J. R.; Smalley, L. L.

    1982-01-01

    General relativity field equations are employed to examine a continuous medium with internal spin. A variational principle formerly applied in the special relativity case is extended to the general relativity case, using a tetrad to express the spin density and the four-velocity of the fluid. An energy-momentum tensor is subsequently defined for a spinning fluid. The equations of motion of the fluid are suggested to be useful in analytical studies of galaxies, for anisotropic Bianchi universes, and for turbulent eddies.

  9. Spin precession in anisotropic cosmologies

    NASA Astrophysics Data System (ADS)

    Kamenshchik, A. Yu.; Teryaev, O. V.

    2016-05-01

    We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. We discuss in some detail the geodesics and the spin precession for both the Kasner and the Heckmann-Schucking solutions. In the Bianchi-IX universe the spin precession acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the very early universe may produce the sterile particles contributing to dark matter.

  10. Spin-manipulating polarized deuterons

    SciTech Connect

    Morozov, V S; Krisch, A D; Leonova, M A; Raymond, R S; Sivers, D W; Wong, V K; Hinterberger, F; Kondratenko, A M; Stephenson, E J

    2011-03-01

    Spin dynamics of polarized deuteron beams near depolarization resonances, including a new polarization preservation concept based on specially-designed multiple resonance crossings, has been tested in a series of experiments in the COSY synchrotron. Intricate spin dynamics with sophisticated pre-programmed patterns as well as effects of multiple crossings of a resonance were studied both theoretically and experimentally with excellent agreement. Possible applications of these results to preserve, manipulate and spin-flip polarized beams in synchrotrons and storage rings are discussed.

  11. Pairing Correlations at High Spins

    NASA Astrophysics Data System (ADS)

    Ma, Hai-Liang; Dong, Bao-Guo; Zhang, Yan; Fan, Ping; Yuan, Da-Qing; Zhu, Shen-Yun; Zhang, Huan-Qiao; Petrache, C. M.; Ragnarsson, I.; Carlsson, B. G.

    The pairing correcting energies at high spins in 161Lu and 138Nd are studied by comparing the results of the cranked-Nilsson-Strutinsky (CNS) and cranked-Nilsson-Strutinsky-Bogoliubov (CNSB) models. It is concluded that the Coriolis effect rather than the rotational alignment effect plays a major role in the reduction of the pairing correlations in the high spin region. Then we proposed an average pairing correction method which not only better reproduces the experimental data comparing with the CNS model but also enables a clean-cut tracing of the configurations thus the full-spin-range discussion on the various rotating bands.

  12. Quantum melting of spin ice

    NASA Astrophysics Data System (ADS)

    Onoda, Shigeki; Tanaka, Yoichi

    2010-03-01

    A quantum melting of the spin ice is proposed for pyrochlore-lattice magnets Pr2TM2O7 (TM =Ir, Zr, and Sn). The quantum pseudospin-1/2 model is derived from the strong-coupling perturbation of the f-p electron transfer in the basis of atomic non-Kramers magnetic doublets. The ground states are characterized by a cooperative ferroquadrupole and pseudospin chirality in the cubic unit cell, forming a magnetic analog of smectic liquid crystals. Then, pinch points observed in spin correlations for dipolar spin-ice systems are replaced with the minima. The relevance to experiments is discussed.

  13. Complexity of vector spin glasses.

    PubMed

    Yeo, J; Moore, M A

    2004-08-13

    We study the annealed complexity of the m-vector spin glasses in the Sherrington-Kirkpatrick limit. The eigenvalue spectrum of the Hessian matrix of the Thouless-Anderson-Palmer free energy is found to consist of a continuous band of positive eigenvalues in addition to an isolated eigenvalue and (m-1) null eigenvalues due to rotational invariance. Rather surprisingly, the band does not extend to zero at any finite temperature. The isolated eigenvalue becomes zero in the thermodynamic limit, as in the Ising case (m=1), indicating that the same supersymmetry breaking recently found in Ising spin glasses occurs in vector spin glasses.

  14. Anomalous Origin of the Left Coronary Artery from the Pulmonary Artery in Adulthood: Challenges and Outcomes

    PubMed Central

    Kothari, Jignesh; Lakhia, Ketav; Solanki, Parth; Parmar, Divyakant; Boraniya, Hiren; Patel, Sanjay

    2016-01-01

    Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is an extremely rare, potentially fatal, congenital anomaly with a high mortality rate in the first year of life. It occurs rarely in adulthood and may appear with malignant ventricular a rrhythmia or sudden death. We report a case of a 49-year-old woman with ALCAPA who presented with dyspnea on exertion. Management was coronary artery bypass grafting to the left anterior descending artery and obtuse marginal arteries, closure of the left main coronary artery ostium, and reestablishment of the dual coronary artery system. PMID:27734000

  15. Spontaneous Recanalization of Superior Mesenteric Artery Occlusion Following Angioplasty and Stenting of Inferior Mesenteric Artery

    SciTech Connect

    Akpinar, Erhan Cil, Barbaros E.; Arat, Anil; Baykal, Atac; Karaman, Kerem; Balkanci, Ferhun

    2006-02-15

    An 84-year-old woman with a history of hypertension and coronary artery disease was admitted with a progressively worsening diffuse abdominal pain. Computed tomography scan of the abdomen and angiography revealed occlusion of the origin and proximal portion of superior mesenteric artery. Aortography also showed severe origin stenosis of inferior mesenteric artery and that the distal part of the superior mesenteric artery was supplied by a prominent marginal artery of Drummond. Patient was effectively treated with percutaneous transluminal angioplasty and stenting of the inferior mesenteric artery. Follow-up imaging studies demonstrated patency of the stent and spontaneous recanalization of superior mesenteric artery occlusion.

  16. Rare anatomic variation of left gastric artery and right hepatic artery in a female cadaver.

    PubMed

    Troupis, Theodore; Chatzikokolis, Stamatis; Zachariadis, Michael; Troupis, George; Anagnostopoulou, Sofia; Skandalakis, Panayiotis

    2008-05-01

    The present report describes a rare case in which the left gastric artery arises directly from the abdominal aorta and the right hepatic artery from the superior mesenteric artery, as observed during the dissection of a female cadaver. The left gastric artery usually rises as one of the three branches of the celiac trunk, which was originally described by Haller in 1756, whereas the right hepatic artery usually originates from the proper hepatic artery. The knowledge of the typical anatomy of the abdominal arteries, and their variations, is especially important due to the numerous interventions performed in the abdominal area.

  17. Secondary arterial hypertension linked to Freon exposure.

    PubMed

    Voge, V M

    1996-05-01

    Freons are generally considered to be minimally toxic. There are no reports in the literature of Freons causing secondary arterial hypertension. We report two cases of acute, massive Freon exposure that preceded secondary arterial hypertension. We hypothesize that the arterial hypertension was precipitated by renal proximal tubular damage, although several other mechanisms are possible.

  18. Peripheral Arterial Disease (P.A.D.)

    MedlinePlus

    ... turn Javascript on. Peripheral Artery Disease (P.A.D.) What is P.A.D.? Arteries Clogged With Plaque Peripheral arterial disease (P. ... button on your keyboard.) Why Is P.A.D. Dangerous? Click for more information Blocked blood flow ...

  19. SPIN-UP/SPIN-DOWN MODELS FOR TYPE Ia SUPERNOVAE

    SciTech Connect

    Stefano, R. Di; Voss, R.

    2011-09-01

    In the single-degenerate scenario for Type Ia supernovae (SNe Ia), a white dwarf (WD) must gain a significant amount of matter from a companion star. Because the accreted mass carries angular momentum, the WD is likely to achieve fast spin periods, which can increase the critical mass, M{sub crit}, needed for explosion. When M{sub crit} is higher than the maximum mass achieved by the WD, the central regions of the WD must spin down before it can explode. This introduces super-Chandrasekhar single-degenerate explosions, and a delay between the completion of mass gain and the time of the explosion. Matter ejected from the binary during mass transfer therefore has a chance to become diffuse, and the explosion occurs in a medium with a density similar to that of typical regions of the interstellar medium. Also, either by the end of the WD's mass increase or else by the time of explosion, the donor may exhaust its stellar envelope and become a WD. This alters, generally diminishing, explosion signatures related to the donor star. Nevertheless, the spin-up/spin-down model is highly predictive. Prior to explosion, progenitors can be super-M{sub Ch} WDs in either wide binaries with WD companions or cataclysmic variables. These systems can be discovered and studied through wide-field surveys. Post-explosion, the spin-up/spin-down model predicts a population of fast-moving WDs, low-mass stars, and even brown dwarfs. In addition, the spin-up/spin-down model provides a paradigm which may be able to explain both the similarities and the diversity observed among SNe Ia.

  20. Spin filter for arbitrary spins by substrate engineering

    NASA Astrophysics Data System (ADS)

    Pal, Biplab; Römer, Rudolf A.; Chakrabarti, Arunava

    2016-08-01

    We design spin filters for particles with potentially arbitrary spin S≤ft(=1/2,1,3/2,\\ldots \\right) using a one-dimensional periodic chain of magnetic atoms as a quantum device. Describing the system within a tight-binding formalism we present an analytical method to unravel the analogy between a one-dimensional magnetic chain and a multi-strand ladder network. This analogy is crucial, and is subsequently exploited to engineer gaps in the energy spectrum by an appropriate choice of the magnetic substrate. We obtain an exact correlation between the magnitude of the spin of the incoming beam of particles and the magnetic moment of the substrate atoms in the chain desired for opening up of a spectral gap. Results of spin polarized transport, calculated within a transfer matrix formalism, are presented for particles having half-integer as well as higher spin states. We find that the chain can be made to act as a quantum device which opens a transmission window only for selected spin components over certain ranges of the Fermi energy, blocking them in the remaining part of the spectrum. The results appear to be robust even when the choice of the substrate atoms deviates substantially from the ideal situation, as verified by extending the ideas to the case of a ‘spin spiral’. Interestingly, the spin spiral geometry, apart from exhibiting the filtering effect, is also seen to act as a device flipping spins—an effect that can be monitored by an interplay of the system size and the period of the spiral. Our scheme is applicable to ultracold quantum gases, and might inspire future experiments in this direction.

  1. Technical considerations for ligation of ruptured hepatic artery aneurysm: is arterial reconstruction necessary?

    PubMed

    Lam, S; Chan, Albert C Y; Poon, Ronnie T P

    2015-06-01

    Ruptured hepatic artery aneurysm is a rare life-threatening condition. Open surgery with ligation of the aneurysm is the treatment of choice if the patient presents with haemodynamic instability. Controversies exist on whether hepatic artery reconstruction is needed after exclusion of the aneurysm. Involvement of the gastroduodenal artery origin was proposed as an indication for reconstruction, but this might be difficult to ascertain upon laparotomy. Recent studies showed that arterial ligation distal to the gastroduodenal artery origin does not necessarily result in ischaemic liver injury, implying that reconstruction in such cases may not be required, especially in a haemodynamically unstable patient. A patient with common hepatic artery aneurysm involving the gastroduodenal artery origin presented with rupture and underwent aneurysm ligation. Adequacy of intrahepatic arterial flow was determined by intra-operative Doppler ultrasonography and arterial reconstruction was not performed. The technical considerations during the operative management of ruptured hepatic artery aneurysms are discussed. PMID:26045071

  2. Vascular Microanatomy of the Pontomedullary Junction, Posterior Inferior Cerebellar Arteries, and the Lateral Spinal Arteries

    PubMed Central

    Mercier, PH.; Brassier, G.; Fournier, H-D; Picquet, J.; Papon, X.; Lasjaunias, P.

    2008-01-01

    Summary This study of 25 brains at the pontomedullary junction defined the different possible origins of the perforating arteries and lateral spinal arteries in relation to the posterior inferior cerebellar arteries (PICAs). - If the PICA emerges from the common trunk of the AICA-PICA coming from the basilar artery, it never gives perforating arteries or a lateral spinal artery on the lateral surface of the brain stem but supplies blood to a part of the ipsilateral cerebellar hemisphere. - If the PICA arises extradurally at C1, it never gives perforating arteries for the lateral surface of the brain stem, but it gives pial branches for the posterior surface of the medulla oblongata and is always the origin of the lateral spinal artery. - If the PICA emerges in the intradural vertebral artery, it is the source of the perforating arteries for the lateral surface of the brain stem and of the blood supply of the ipsilateral cerebellum. PMID:20557786

  3. Compliant transducer measures artery profile

    NASA Technical Reports Server (NTRS)

    Feldstein, C.; Culler, V. H.; Crawford, D. W.; Spears, J. R.

    1981-01-01

    Instrument consisting of compliant fingers with attached semiconductor pickups measures inside contours of narrow vessels. Instrument, originally designed to monitor human arteries, is drawn through vessel to allow finges to follow contours. Lead wires transmit electrical signals to external processing equipment.

  4. Photonic sensing of arterial distension

    PubMed Central

    Ruh, Dominic; Subramanian, Sivaraman; Sherman, Stanislav; Ruhhammer, Johannes; Theodor, Michael; Dirk, Lebrecht; Foerster, Katharina; Heilmann, Claudia; Beyersdorf, Friedhelm; Zappe, Hans; Seifert, Andreas

    2016-01-01

    Most cardiovascular diseases, such as arteriosclerosis and hypertension, are directly linked to pathological changes in hemodynamics, i.e. the complex coupling of blood pressure, blood flow and arterial distension. To improve the current understanding of cardiovascular diseases and pave the way for novel cardiovascular diagnostics, innovative tools are required that measure pressure, flow, and distension waveforms with yet unattained spatiotemporal resolution. In this context, miniaturized implantable solutions for continuously measuring these parameters over the long-term are of particular interest. We present here an implantable photonic sensor system capable of sensing arterial wall movements of a few hundred microns in vivo with sub-micron resolution, a precision in the micrometer range and a temporal resolution of 10 kHz. The photonic measurement principle is based on transmission photoplethysmography with stretchable optoelectronic sensors applied directly to large systemic arteries. The presented photonic sensor system expands the toolbox of cardiovascular measurement techniques and makes these key vital parameters continuously accessible over the long-term. In the near term, this new approach offers a tool for clinical research, and as a perspective, a continuous long-term monitoring system that enables novel diagnostic methods in arteriosclerosis and hypertension research that follow the trend in quantifying cardiovascular diseases by measuring arterial stiffness and more generally analyzing pulse contours. PMID:27699095

  5. Bilateral internal thoracic artery grafting

    PubMed Central

    2013-01-01

    The effectiveness of the left internal mammary artery graft to the anterior descending coronary artery as a surgical strategy has been shown to improve the survival rate and decrease the risk of adverse cardiac events in patients undergoing coronary bypass surgery. These clinical benefits appear to be related to the superior short and long-term patency rates of the internal thoracic artery graft. Although the advantages of using of both internal thoracic arteries (ITA) for bypass grafting have taken longer to prove, recent results from multiple data sets now support these findings. The major advantage of bilateral ITA grafting appears to be improved survival rate, while the disadvantages of complex ITA grafting include the increased complexity of operation, and an increased risk of wound complications. While these short-term disadvantages have been mitigated in contemporary surgical practice, they have not eliminated. Bilateral ITA grafting should be considered the procedure of choice for patients undergoing coronary bypass surgery that have a predicted survival rate of longer than ten years. PMID:23977627

  6. Engineering of arteries in vitro

    PubMed Central

    Huang, Angela H.; Niklason, Laura E.

    2014-01-01

    This review will focus on two elements that are essential for functional arterial regeneration in vitro: the mechanical environment and the bioreactors used for tissue growth. The importance of the mechanical environment to embryological development, vascular functionality, and vascular graft regeneration will be discussed. Bioreactors generate mechanical stimuli to simulate the biomechanical environment of the arterial system. This system has been used to reconstruct arterial grafts with appropriate mechanical strength for implantation by controlling the chemical and mechanical environments in which the grafts are grown. Bioreactors are powerful tools to study the effect of mechanical stimuli on extracellular matrix (ECM) architecture and the mechanical properties of engineered vessels. Hence biomimetic systems enable us to optimize chemo-biomechanical culture conditions to regenerate engineered vessels with physiological properties similar to those of native arterial vessels. In addition, this review will introduce and examine various approaches and techniques that have been used to engineer biologically-based vascular grafts, including collagen-based grafts, fibrin-gel grafts, cell sheet engineering, biodegradable polymers, and decellularization of native vessels. PMID:24399290

  7. Photonic sensing of arterial distension

    PubMed Central

    Ruh, Dominic; Subramanian, Sivaraman; Sherman, Stanislav; Ruhhammer, Johannes; Theodor, Michael; Dirk, Lebrecht; Foerster, Katharina; Heilmann, Claudia; Beyersdorf, Friedhelm; Zappe, Hans; Seifert, Andreas

    2016-01-01

    Most cardiovascular diseases, such as arteriosclerosis and hypertension, are directly linked to pathological changes in hemodynamics, i.e. the complex coupling of blood pressure, blood flow and arterial distension. To improve the current understanding of cardiovascular diseases and pave the way for novel cardiovascular diagnostics, innovative tools are required that measure pressure, flow, and distension waveforms with yet unattained spatiotemporal resolution. In this context, miniaturized implantable solutions for continuously measuring these parameters over the long-term are of particular interest. We present here an implantable photonic sensor system capable of sensing arterial wall movements of a few hundred microns in vivo with sub-micron resolution, a precision in the micrometer range and a temporal resolution of 10 kHz. The photonic measurement principle is based on transmission photoplethysmography with stretchable optoelectronic sensors applied directly to large systemic arteries. The presented photonic sensor system expands the toolbox of cardiovascular measurement techniques and makes these key vital parameters continuously accessible over the long-term. In the near term, this new approach offers a tool for clinical research, and as a perspective, a continuous long-term monitoring system that enables novel diagnostic methods in arteriosclerosis and hypertension research that follow the trend in quantifying cardiovascular diseases by measuring arterial stiffness and more generally analyzing pulse contours.

  8. [PREDICTORS OF RESISTANT ARTERIAL HYPERTENSION].

    PubMed

    Lazutkina, A Y; Gorbunov, V V

    2016-01-01

    The paper reports results of 6 year prospective observation of 7959 members of locomotive crews engaged at the Transbaikal Railways. The study aimed to estimate the probability and time of development of resistant arterial hypertension under effect of predictors of this disease. The data obtained are of value for diagnostic, prophylactic, and therapeutic practice. PMID:27522725

  9. Muon spin relaxation in spin glass PdMn

    SciTech Connect

    Heffner, R.H.; Leon, M.; Schillaci, M.E.; Dodds, S.A.; Gist, G.A.; MacLaughlin, D.E.; Mydosh, J.A.; Nieuwenhuys, G.J.

    1983-01-01

    Muon spin relaxation (..mu..SR) rates have been measured in transverse, longitudinal, and zero applied field for the spin glass PdMn (7 at. %), and are compared with a previous study of the disordered ferromagnet PdMn (2 at. %). The calculated paramagnetic state transverse field relaxation rate for noninteracting spins is much larger than the observed rate in spin glass PdMn, but is in good agreement with ferromagnetic PdMn. The zero field relaxation rate shows a sharp cusp at T/sub g/=5K. An applied longitudinal field of 5 kG is insufficient to suppress this cusp in spin glss PdMn, but will suppress a similar cusp in ferromagnetic PdMn. Below T/sub g/=5K. An applied longitudinal field of 5 kG is insufficient to suppress this cusp in spin glass PdMn, but will suppress a similar cusp in ferromagnetic PdMn. Below T/sub g/, a distribution of quasistatic local fields is observed in zero field, which has the same temperature dependence for both samples. Comparisons with model calculations are discussed.

  10. Random SU(2)-symmetric spin-S chains

    NASA Astrophysics Data System (ADS)

    Quito, V. L.; Hoyos, José A.; Miranda, E.

    2016-08-01

    We study the low-energy physics of a broad class of time-reversal invariant and SU(2)-symmetric one-dimensional spin-S systems in the presence of quenched disorder via a strong-disorder renormalization-group technique. We show that, in general, there is an antiferromagnetic phase with an emergent SU (2 S +1 ) symmetry. The ground state of this phase is a random singlet state in which the singlets are formed by pairs of spins. For integer spins, there is an additional antiferromagnetic phase which does not exhibit any emergent symmetry (except for S =1 ). The corresponding ground state is a random singlet one but the singlets are formed mostly by trios of spins. In each case the corresponding low-energy dynamics is activated, i.e., with a formally infinite dynamical exponent, and related to distinct infinite-randomness fixed points. The phase diagram has two other phases with ferromagnetic tendencies: a disordered ferromagnetic phase and a large spin phase in which the effective disorder is asymptotically finite. In the latter case, the dynamical scaling is governed by a conventional power law with a finite dynamical exponent.

  11. Spin voltage generation through optical excitation of complementary spin populations.

    PubMed

    Bottegoni, Federico; Celebrano, Michele; Bollani, Monica; Biagioni, Paolo; Isella, Giovanni; Ciccacci, Franco; Finazzi, Marco

    2014-08-01

    By exploiting the spin degree of freedom of carriers inside electronic devices, spintronics has a huge potential for quantum computation and dissipationless interconnects. Pure spin currents in spintronic devices should be driven by a spin voltage generator, able to drive the spin distribution out of equilibrium without inducing charge currents. Ideally, such a generator should operate at room temperature, be highly integrable with existing semiconductor technology, and not interfere with other spintronic building blocks that make use of ferromagnetic materials. Here we demonstrate a device that matches these requirements by realizing the spintronic equivalent of a photovoltaic generator. Whereas a photovoltaic generator spatially separates photoexcited electrons and holes, our device exploits circularly polarized light to produce two spatially well-defined electron populations with opposite in-plane spin projections. This is achieved by modulating the phase and amplitude of the light wavefronts entering a semiconductor (germanium) with a patterned metal overlayer (platinum). The resulting light diffraction pattern features a spatially modulated chirality inside the semiconductor, which locally excites spin-polarized electrons thanks to electric dipole selection rules. PMID:24952750

  12. The Right Gastroepiploic Artery Graft for Coronary Artery Bypass Grafting: A 30-Year Experience

    PubMed Central

    Suma, Hisayoshi

    2016-01-01

    Throughout its 30-year history, the right gastroepiploic artery (GEA) has been useful for in situ grafts in coronary artery bypass grafting (CABG). The early graft patency rate is high, and the late patency rate has improved by using the skeletonized GEA graft and proper target selection, which involves having a target coronary artery with a tight >90% stenosis. Total arterial revascularization with the internal thoracic artery and GEA grafts is an option for achieving better outcomes from CABG procedures. PMID:27525230

  13. Missed Total Occlusion Due to the Occipital Artery Arising from the Internal Carotid Artery

    SciTech Connect

    Ustunsoz, Bahri Gumus, Burcak; Koksal, Ali; Koroglu, Mert; Akhan, Okan

    2007-02-15

    A 56-year-old man was referred for digital subtraction angiography (DSA) with an ultrasound diagnosis of right proximal internal carotid artery (ICA) stenosis for possible carotid artery stenting. DSA revealed total occlusion of the ICA and an occipital artery arising from the stump and simulating continuation of the ICA. An ascending pharyngeal artery also arose from the same occipital artery. This case is of interest because this is a rare variation besides being a cause of misdiagnosis at carotid ultrasound.

  14. RESEARCH PLAN FOR SPIN PHYSICS AT RHIC.

    SciTech Connect

    AIDALA, C.; BUNCE, G.; ET AL.

    2005-02-01

    In this report we present the research plan for the RHIC spin program. The report covers (1) the science of the RHIC spin program in a world-wide context; (2) the collider performance requirements for the RHIC spin program; (3) the detector upgrades required, including timelines; (4) time evolution of the spin program.

  15. Intra-arterial chemotherapy for bilateral retinoblastoma via left ophthalmic artery and right anterior deep temporal artery

    PubMed Central

    Amans, Matthew R; Narvid, Jared; Halbach, Van V

    2014-01-01

    A 12-month-old boy with a history of bilateral retinoblastoma refractory to systemic chemotherapy, laser therapy and cryotherapy, with excellent response to previous intra-arterial melphalan infusion, presents with active tumour deposits in the right eye. Repeat intra-arterial chemotherapy was recommended. Previous bilateral melphalan infusion was uneventful using flow-guided catheterisation technique. Direct catheterisation of the right ophthalmic artery was unsuccessful despite employment of several flow-guided and over-the-wire catheters. Superselective catheterisation of the ipsilateral middle meningeal artery was unable to identify an anastomotic connection to the ophthalmic artery; however, angiography of the anterior deep temporal artery identified an alternate route for chemotherapy infusion. The anterior deep temporal artery was successfully and safely catheterised to infuse chemotherapy into the ophthalmic artery. The anterior deep temporal artery is an important potential anastomotic connection to the ophthalmic artery that can be used safely and effectively for central retinal artery chemotherapy infusion for retinoblastoma treatment. PMID:25240013

  16. Anisotropic spin dephasing of impurity-bound electron spins in ZnO

    SciTech Connect

    Lee, Jieun; Sih, Vanessa; Venugopal, Aneesh

    2015-01-05

    We investigate the electron spin dynamics of n-type c-axis oriented bulk zinc oxide (ZnO) by using time-resolved Kerr rotation and resonant spin amplification measurements. Calculating resonant spin amplification using an anisotropic spin dephasing model reveals that there are two species involved in the spin dynamics, which we attribute to conduction and impurity-bound electron spins, respectively. We find that the impurity-bound electron spin dephasing mechanism is strongly anisotropic due to anisotropic exchange interactions. The identification of the two spin species and their dephasing mechanisms is further supported by the temperature, power, and wavelength dependence of the spin coherence measurements.

  17. Magnetoelectric control of spin currents

    NASA Astrophysics Data System (ADS)

    Gómez, J. E.; Vargas, J. M.; Avilés-Félix, L.; Butera, A.

    2016-06-01

    The ability to control the spin current injection has been explored on a hybrid magnetoelectric system consisting of a (011)-cut ferroelectric lead magnesium niobate-lead titanate (PMNT) single crystal, a ferromagnetic FePt alloy, and a metallic Pt. With this PMNT/FePt/Pt structure we have been able to control the magnetic field position or the microwave excitation frequency at which the spin pumping phenomenon between FePt and Pt occurs. We demonstrate that the magnetoelectric heterostructure operating in the L-T (longitudinal magnetized-transverse polarized) mode couples the PMNT crystal to the magnetostrictive FePt/Pt bilayer, displaying a strong magnetoelectric coefficient of ˜140 Oe cm kV-1. Our results show that this mechanism can be effectively exploited as a tunable spin current intensity emitter and open the possibility to create an oscillating or a bistable switch to effectively manipulate spin currents.

  18. Spinning angle optical calibration apparatus

    DOEpatents

    Beer, Stephen K.; Pratt, II, Harold R.

    1991-01-01

    An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting an accurate reproducing of spinning "magic angles" in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the "magic angle" of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning "magic angle" of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position.

  19. Experimenting with a Spinning Disk

    ERIC Educational Resources Information Center

    Cross, Rod

    2015-01-01

    Almost everyone will have observed a spinning coin fall to a shuddering stop. How and why does it do that? Several experiments are described, suitable for a student project, to help motivate an understanding of the rotational dynamics involved.

  20. Spinning angle optical calibration apparatus

    SciTech Connect

    Beer, S.K.; Pratt, H.R. II.

    1989-09-12

    An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting and accurate reproducing of spinning magic angles in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the magic angle of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning magic angle of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position. 2 figs.

  1. Spin models of the proton

    SciTech Connect

    Ramsey, G.P.

    1988-10-20

    We have constructed a model of the proton spin based on a broken SU(6) parameterization for the spin-weighted valence quark distributions in a longitudinally polarized proton. The polarized sea and gluon distributions are assumed to have simple relations to the corresponding unpolarized structure functions. The sum rules, which involve the non-singlet components of the structure function xg/sub 1/, imply that the valence quarks carry about 78% of the proton spin, while the spin carried by sea quarks is negative. Recent EMC data suggest a model in which the sea quarks carry a large negative polarization, whereas certain theoretical arguments favor a model with a smaller negatively polarized sea. These models are discussed with reference to the sum rules. Experiments are suggested which will discriminate between these models. 24 refs., 4 figs.

  2. Spin transport in graphene superlattice under strain

    NASA Astrophysics Data System (ADS)

    Sattari, Farhad

    2016-09-01

    In this paper, the spin-dependent transport and the spin polarization properties for graphene superlattice with Rashba spin-orbit interaction (RSOI) in the presence of zigzag and armchair direction strain are studied. It is found that for the zigzag direction strain the angular range of the spin-inversion can be efficiently controlled by the strain strength. In addition, the efficiency of spin-inversion and spin-dependent conductivity decreases by increasing the strain strength. When the armchair direction strain is applied to a monolayer graphene superlattice the spin polarization can be observed and increases by increasing the strain strength, whereas for the zigzag direction strain it is zero.

  3. Spin current source based on a quantum point contact with local spin-orbit interaction

    SciTech Connect

    Nowak, M. P.; Szafran, B.

    2013-11-11

    Proposal for construction of a source of spin-polarized current based on quantum point contact (QPC) with local spin-orbit interaction is presented. We show that spin-orbit interaction present within the narrowing acts like a spin filter. The spin polarization of the current is discussed as a function of the Fermi energy and the width of the QPC.

  4. Muon spin rotation in solids

    NASA Technical Reports Server (NTRS)

    Stronach, C. E.

    1983-01-01

    The muon spin rotation (MuSR) technique is used to probe the microscopic electron density in materials. High temperature MuSR and magnetization measurements in nickel are in progress to allow an unambiguous determination of the muon impurity interaction and the impurity induced change in local spin density. The first results on uniaxial stress induced frequency shifts in an Fe single crystal are also reported.

  5. Hybrid spin-crossover nanostructures

    PubMed Central

    Quintero, Carlos M; Félix, Gautier; Suleimanov, Iurii; Sánchez Costa, José; Molnár, Gábor; Salmon, Lionel; Nicolazzi, William

    2014-01-01

    Summary This review reports on the recent progress in the synthesis, modelling and application of hybrid spin-crossover materials, including core–shell nanoparticles and multilayer thin films or nanopatterns. These systems combine, often in synergy, different physical properties (optical, magnetic, mechanical and electrical) of their constituents with the switching properties of spin-crossover complexes, providing access to materials with unprecedented capabilities. PMID:25551051

  6. Brachiocephalic artery thrombosis in adult nephrotic syndrome

    PubMed Central

    Brahmbhatt, B. K.; Mathew, A.; Rajesh, R.; Kurian, G.; Unni, V. N.

    2011-01-01

    Thrombotic events are known to occur in nephrotic syndrome, as these patients have a hypercoagulable state. Venous thrombosis is well recognized, but arterial thrombosis is rare and is mainly noted in pediatric population. In the present study, we report a case of thrombosis of right brachiocephalic artery, embolic occlusion of right axillary artery, and right middle cerebral artery territory infarction due to thromboembolism in an adult patient with nephrotic syndrome (Minimal change disease). Patient underwent thromboembolectomy in the right axillary artery followed by anticoagulation therapy. PMID:21886984

  7. Ruptured retinal arterial macroaneurysm: diagnosis and management.

    PubMed

    Speilburg, Ashley M; Klemencic, Stephanie A

    2014-01-01

    Retinal arterial macroaneurysm is an acquired, focal dilation of a retinal artery, typically occurring within the first three bifurcations of the central retinal artery. The clinical presentation of a retinal arterial macroaneurysm is highly variable, making initial diagnosis difficult and differentials many. Identification of retinal arterial macroaneurysms is crucial to appropriately co-manage with the primary care physician for hypertension control. Prognosis is generally good and observation is often an adequate treatment. However, in cases of macular threat or involvement, some treatment options are available and referral to a retinal specialist is indicated.

  8. Two Wien Filter Spin Flipper

    SciTech Connect

    Grames, J M; Benesch, J F; Clark, J; Hansknecht, J; Kazimi, R; Machie, D; Poelker, M; Stutzman, M L; Suleiman, R; Zhang, Y

    2011-03-01

    A new 4pi spin manipulator composed of two Wien filters oriented orthogonally and separated by two solenoids has been installed at the CEBAF/Jefferson Lab photoinjector. The new spin manipulator is used to precisely set the electron spin direction at an experiment in any direction (in or out of plane of the accelerator) and provides the means to reverse, or flip, the helicity of the electron beam on a daily basis. This reversal is being employed to suppress systematic false asymmetries that can jeopardize challenging parity violation experiments that strive to measure increasingly small physics asymmetries [*,**,***]. The spin manipulator is part of the ultra-high vacuum polarized electron source beam line and has been successfully operated with 100keV and 130keV electron beam at high current (>100 microAmps). A unique feature of the device is that spin-flipping requires only the polarity of one solenoid magnet be changed. Performance characteristics of the Two Wien Filter Spin Flipper will be summarized.

  9. Photonic spin filter with dielectric metasurfaces.

    PubMed

    Ke, Yougang; Liu, Yachao; Zhou, Junxiao; Liu, Yuanyuan; Luo, Hailu; Wen, Shuangchun

    2015-12-28

    We propose a photonic spin filter whose structure is similar to that of conventional spatial filter, but the two plano-convex lenses are replaced by Pancharatnam-Berry phase ones. The dielectric metasurface with high transmission and conversion efficiency is designed to work as Pancharatnam-Berry phase lens. The photonic spin filter can sort desired spin photons from the input beam with mixed spin states, and thereby facilitate possible applications in spin-based photonics. PMID:26831976

  10. Spin selective filtering of polariton condensate flow

    SciTech Connect

    Gao, T.; Antón, C.; Martín, M. D.; Liew, T. C. H.; Hatzopoulos, Z.; Viña, L.; Eldridge, P. S.; Savvidis, P. G.

    2015-07-06

    Spin-selective spatial filtering of propagating polariton condensates, using a controllable spin-dependent gating barrier, in a one-dimensional semiconductor microcavity ridge waveguide is reported. A nonresonant laser beam provides the source of propagating polaritons, while a second circularly polarized weak beam imprints a spin dependent potential barrier, which gates the polariton flow and generates polariton spin currents. A complete spin-based control over the blocked and transmitted polaritons is obtained by varying the gate polarization.

  11. Spin stabilized magnetic levitation of horizontal rotors.

    SciTech Connect

    Romero, Louis Anthony

    2004-10-01

    In this paper we present an analysis of a new configuration for achieving spin stabilized magnetic levitation. In the classical configuration, the rotor spins about a vertical axis; and the spin stabilizes the lateral instability of the top in the magnetic field. In this new configuration the rotor spins about a horizontal axis; and the spin stabilizes the axial instability of the top in the magnetic field.

  12. Kane model parameters and stochastic spin current

    NASA Astrophysics Data System (ADS)

    Chowdhury, Debashree

    2015-11-01

    The spin current and spin conductivity is computed through thermally driven stochastic process. By evaluating the Kramers equation and with the help of k → . p → method we have studied the spin Hall scenario. Due to the thermal assistance, the Kane model parameters get modified, which consequently modulate the spin orbit coupling (SOC). This modified SOC causes the spin current to change in a finite amount.

  13. [Accessory renal arteries in human fetuses].

    PubMed

    Gościcka, D; Szpinda, M; Kochan, J

    1996-12-01

    Using conventional anatomical methods, renal arteries of 140 human fetuses were studied. It was found (21.1%) that the accessory renal arteries occurred in a three-fold manner: 1. as single arteries (19.2%), 2. as double arteries (2.1%) and 3. as triplex arteries (0.7%). More often they originated from the right part of the circumference of the abdominal aorta, mainly in the female fetuses. These arteries penetrated the following segments of the kidney: the inferior (12.9%), the superior (2.3%), the anterior inferior (2.8%), the posterior (2.1%) and the anterior superior (1.5%). They crossed the renal pelvis more often in front (12.2%) than from behind of it (5%). The frequency of the occurrence of the accessory arteries depends not from the age of the fetus. PMID:9082875

  14. Experimental evidence of the compressibility of arteries.

    PubMed

    Yosibash, Zohar; Manor, Itay; Gilad, Ilan; Willentz, Udi

    2014-11-01

    A definitive answer to the question whether artery walls are incompressible is to our opinion not yet categorically provided. Experimental-based evidence on the level of compressibility in artery walls is not easily achieved because of the difficulties associated with the measurement of very small differences in volumes under physiological pressure in these biological tissues. Past experiments aimed at addressing the question considered different species, different arteries, the experimental devices were not accurate enough and a statistical analysis of the results was missing. A precise experimental device together with a thorough testing protocol, a careful selection of arteries and a statistical analysis is presented for a definitive evaluation of the artery wall compressibility. We provide experimental evidence that in saphenous and femoral porcine arteries under physiological pressure range a relative compressibility of 2-6% is observed. The pre-assumption of incompressibility in many phenomenological constitutive models of artery walls should probably be re-evaluated.

  15. Pulmonary Artery Intimal Sarcoma: A Case Report

    PubMed Central

    Kriz, Joseph P.; Munfakh, Nabil A.; King, Gregory S.; Carden, Juan O.

    2016-01-01

    Pulmonary artery intimal sarcomas are rare and lethal malignant tumors that typically affect larger vessels: the aorta, inferior vena cava, and pulmonary arteries. Since symptoms and imaging of pulmonary arterial intimal sarcomas mimic pulmonary thromboembolism, the differential diagnosis of a patient presenting with chest pain, dyspnea, and filling defect within the pulmonary arteries should include intimal sarcoma. Often right ventricular failure is observed due to pulmonary hypertension caused by the obstructive effect of the tumor and concomitant chronic thromboembolism. We report the case of a 72-year-old African-American male with arterial intimal sarcoma of the left and right pulmonary artery with extension through the right artery into the bronchus and right lung. PMID:27239183

  16. Physiologic assessment of coronary artery fistula

    SciTech Connect

    Gupta, N.C.; Beauvais, J. )

    1991-01-01

    Coronary artery fistula is an uncommon clinical entity. The most common coronary artery fistula is from the right coronary artery to the right side of the heart, and it is less frequent to the pulmonary artery. The effect of a coronary artery fistula may be physiologically significant because of the steal phenomenon resulting in coronary ischemia. Based on published reports, it is recommended that patients with congenital coronary artery fistulas be considered candidates for elective surgical correction to prevent complications including development of congestive heart failure, angina, subacute bacterial endocarditis, myocardial infarction, and coronary aneurysm formation with rupture or embolization. A patient is presented in whom treadmill-exercise thallium imaging was effective in determining the degree of coronary steal from a coronary artery fistula, leading to successful corrective surgery.

  17. Arterial endothelial function measurement method and apparatus

    DOEpatents

    Maltz, Jonathan S; Budinger, Thomas F

    2014-03-04

    A "relaxoscope" (100) detects the degree of arterial endothelial function. Impairment of arterial endothelial function is an early event in atherosclerosis and correlates with the major risk factors for cardiovascular disease. An artery (115), such as the brachial artery (BA) is measured for diameter before and after several minutes of either vasoconstriction or vasorelaxation. The change in arterial diameter is a measure of flow-mediated vasomodification (FMVM). The relaxoscope induces an artificial pulse (128) at a superficial radial artery (115) via a linear actuator (120). An ultrasonic Doppler stethoscope (130) detects this pulse 10-20 cm proximal to the point of pulse induction (125). The delay between pulse application and detection provides the pulse transit time (PTT). By measuring PTT before (160) and after arterial diameter change (170), FMVM may be measured based on the changes in PTT caused by changes in vessel caliber, smooth muscle tone and wall thickness.

  18. Proinflammation: The Key to Arterial Aging

    PubMed Central

    Wang, Mingyi; Jiang, Liqun; Monticone, Robert E.; Lakatta, Edward G.

    2014-01-01

    Arterial aging is the major contributing factor to increases in the incidence and prevalence of cardiovascular disease, due mainly to the presence of chronic, low-grade, “sterile” arterial inflammation. Inflammatory signaling driven by the angiotensin II cascade perpetrates adverse age-associated arterial structural and functional remodeling. The aged artery is characterized by endothelial disruption, enhanced vascular smooth muscle cell migration and proliferation, extracellular matrix deposition, elastin fracture, and matrix calcification/amyloidosis/glycation. Importantly, the molecular mechanisms of arterial aging are also relevant to the pathogenesis of hypertension, and atherosclerosis. Age-associated arterial proinflammation is, to some extent, mutable, and interventions to suppress or delay it may have the potential to ameliorate or retard age-associated arterial diseases. PMID:24365513

  19. Netrin-1 controls sympathetic arterial innervation

    PubMed Central

    Brunet, Isabelle; Gordon, Emma; Han, Jinah; Cristofaro, Brunella; Broqueres-You, Dong; Liu, Chun; Bouvrée, Karine; Zhang, Jiasheng; del Toro, Raquel; Mathivet, Thomas; Larrivée, Bruno; Jagu, Julia; Pibouin-Fragner, Laurence; Pardanaud, Luc; Machado, Maria J.C.; Kennedy, Timothy E.; Zhuang, Zhen; Simons, Michael; Levy, Bernard I.; Tessier-Lavigne, Marc; Grenz, Almut; Eltzschig, Holger; Eichmann, Anne

    2014-01-01

    Autonomic sympathetic nerves innervate peripheral resistance arteries, thereby regulating vascular tone and controlling blood supply to organs. Despite the fundamental importance of blood flow control, how sympathetic arterial innervation develops remains largely unknown. Here, we identified the axon guidance cue netrin-1 as an essential factor required for development of arterial innervation in mice. Netrin-1 was produced by arterial smooth muscle cells (SMCs) at the onset of innervation, and arterial innervation required the interaction of netrin-1 with its receptor, deleted in colorectal cancer (DCC), on sympathetic growth cones. Function-blocking approaches, including cell type–specific deletion of the genes encoding Ntn1 in SMCs and Dcc in sympathetic neurons, led to severe and selective reduction of sympathetic innervation and to defective vasoconstriction in resistance arteries. These findings indicate that netrin-1 and DCC are critical for the control of arterial innervation and blood flow regulation in peripheral organs. PMID:24937433

  20. Ballistic spin resonance in multisubband quantum wires

    NASA Astrophysics Data System (ADS)

    Hachiya, Marco O.; Usaj, Gonzalo; Egues, J. Carlos

    2014-03-01

    Ballistic spin resonance was experimentally observed in a quasi-one-dimensional wire by Frolov et al. [Nature (London) 458, 868 (2009), 10.1038/nature07873]. The spin resonance was generated by a combination of an external static magnetic field and the oscillating effective spin-orbit magnetic field due to periodic bouncings of the electrons off the boundaries of a narrow channel. An increase of the D'yakonov-Perel spin relaxation rate was observed when the frequency of the spin-orbit field matched that of the Larmor precession frequency around the external magnetic field. Here we develop a model to account for the D'yakonov-Perel mechanism in multisubband quantum wires with both the Rashba and Dresselhaus spin-orbit interactions. Considering elastic spin-conserving impurity scatterings in the time-evolution operator (Heisenberg representation), we extract the spin relaxation time by evaluating the time-dependent expectation value of the spin operators. The magnetic field dependence of the nonlocal voltage, which is related to the spin relaxation time behavior, shows a wide plateau, in agreement with the experimental observation. This plateau arises due to injection in higher subbands and small-angle scattering. In this quantum mechanical approach, the spin resonance occurs near the spin-orbit-induced energy anticrossings of the quantum wire subbands with opposite spins. We also predict anomalous dips in the spin relaxation time as a function of the magnetic field in systems with strong spin-orbit couplings.

  1. Observation of large spin accumulation voltages in nondegenerate Si spin devices due to spin drift effect: Experiments and theory

    NASA Astrophysics Data System (ADS)

    Tahara, Takayuki; Ando, Yuichiro; Kameno, Makoto; Koike, Hayato; Tanaka, Kazuhito; Miwa, Shinji; Suzuki, Yoshishige; Sasaki, Tomoyuki; Oikawa, Tohru; Shiraishi, Masashi

    2016-06-01

    A large spin accumulation voltage of more than 1.5 mV at 1 mA, i.e., a magnetoresistance of 1.5 Ω, was measured by means of the local three-terminal magnetoresistance in nondegenerate Si-based lateral spin valves (LSVs) at room temperature. This is the largest spin accumulation voltage measured in semiconductor-based LSVs. The modified spin drift-diffusion model, which successfully accounts for the spin drift effect, explains the large spin accumulation voltage and significant bias-current-polarity dependence. The model also shows that the spin drift effect enhances the spin-dependent magnetoresistance in the electric two-terminal scheme. This finding provides a useful guiding principle for spin metal-oxide-semiconductor field-effect transistor operations.

  2. Longitudinal spin dynamics in ferrimagnets: Multiple spin wave nature of longitudinal spin excitations

    NASA Astrophysics Data System (ADS)

    Krivoruchko, V. N.

    2016-08-01

    Motivated by the existing controversy about the physical mechanisms that govern longitudinal magnetization dynamics under the effect of ultrafast laser pulses, in this paper we study the microscopic model of longitudinal spin excitations in a two-sublattice ferrimagnet using the diagrammatic technique for spin operators. The diagrammatic approach provides us with an efficient procedure to derive graphical representations for perturbation expansion series for different spin Green's functions and thus to overcome limitations typical for phenomenological approaches. The infinite series involving all distinct loops built from spin wave propagators are summed up. These result in an expression for the longitudinal spin susceptibility χz z(q ,ω ) applicable in all regions of frequency ω and wave vector q space beyond the hydrodynamical and critical regimes. A strong renormalization of the longitudinal spin oscillations due to processes of virtual creation and annihilation of transverse spin waves has been found. We have shown that the spectrum of longitudinal excitations consists of a quasirelaxation mode forming a central peak in χz z(q ,ω ) and two (acoustic and exchange) precessionlike modes. As the main result, it is predicted that both acoustic and exchange longitudinal excitations are energetically above similar modes of transverse spin waves at the same temperature and wave vector. The existence of the exchange longitudinal mode at such frequencies can result in a new form of excitation behavior in ferrimagnetic system, which could be important for understanding the physics of nonequilibrium magnetic dynamics under the effect of ultrafast laser pulses in multisublattice magnetic materials.

  3. Hyperdensity of the Basilar Artery on Postmortem CT: A Potential Indicator for Basilar Artery Thrombosis.

    PubMed

    Garland, Jack; Tse, Rexson; Beh, Raymond J; Lyons, Timothy J; Cala, Allan D

    2016-06-01

    Basilar artery thrombosis constitutes 1% of all types of stroke, carries a mortality rate of up to 90%, and is one of the rarer causes of sudden death. It leads to brain stem ischemia and commonly presents with impaired consciousness, cranial nerve palsy, hemiplegia or quadriplegia, and sudden collapse. Clinically, the diagnosis of basilar artery thrombosis is made on clinical symptoms, along with a hyperdense basilar artery in antemortem computed tomography (CT) scan. To our knowledge, whether a hyperdense basilar artery indicates basilar artery thrombosis on postmortem CT scan is not documented in the literature. We present a case report of a 55-year-old man who on postmortem CT scan showed a hyperdense basilar artery and was subsequently confirmed to be a fatal basilar artery thrombosis. We suggest that a hyperdense basilar artery on postmortem CT should prompt the pathologist to consider basilar artery thrombosis. PMID:27049662

  4. Spin Waves and Spin Relaxation in Normal Fermi Liquids.

    NASA Astrophysics Data System (ADS)

    Meltzer, David Elliott

    This work explores several aspects of spin-dependent excitations in normal Fermi liquids. Chapter 1 is a general introduction and overview of the work. The Landau kinetic equation and its application to nonequilibrium proper- ties of Fermi liquids is discussed, and the properties of collective density modes are briefly reviewed. The properties of both longitu- dinal and transverse spin excitations are then outlined, leading up to a discussion of spin waves and spin diffusion, including the Leggett -Rice effect. Chapter 2 discusses the possibility of making a determination of the contribution of many-body interactions to the large effective mass in "heavy-fermion" materials, e.g. UPt(,3), by the method of conduction-electron spin resonance (CESR). It is shown that a microwave trans- mission observation of CESR might show a resonance pattern which, based on already measured parameters, would clearly distinguish among various suggested models for the strength of the many-body effects. Chapter 3 investigates the accuracy of the usual relaxation time approximations, involving the spin diffusion lifetime (tau)(,D), which are generally made in analyses of spin waves and the Leggett-Rice effect in Fermi liquids. By employing the variational methods of Ah-Sam, H(SLASHCIRC)jgaard -Jensen and Smith, and Egilsson and Pethick, we are able to determine upper and lower bounds on the effective diffusion coefficient resulting from spin wave phenomena which are accurate in the whole Fermi liquid regime. Our results indicate that the usual approximations break down for(' )T < 7 mK in ('3)He, but are accurate to within (TURN)2% in 5% ('3)He-('4)He mixtures. Chapter 4 contains a calculation of the longitudinal spin relaxa- tion time T(,1) in bulk ('3)He in the Fermi liquid (T << T(,F)) regime. The kinetic equation is used to obtain an expression for T(,1) in terms of perturbations of the scattering amplitude. These perturbations are then obtained using the induced interaction model

  5. Arterial blood pressure wave forms in radial and posterior tibial arteries in critically ill newborn infants.

    PubMed

    Gevers, M; Hack, W W; Ree, E F; Lafeber, H N; Westerhof, N

    1993-04-01

    The aim of this study was to document arterial blood pressure wave forms at two sites along the arterial tree of the neonate: in the radial and posterior tibial arteries. Using a high-fidelity catheter tip-transducer system, peripheral arterial blood pressure wave forms in 26 critically newborn infants were studied. In 14 infants the radial artery and in 12 infants the posterior tibial artery was cannulated. Radial artery blood pressure waves resembled those of proximal aortic rather than those of the radial artery in adults. Quantitative analysis of the waves was performed to reassure this finding. Blood pressure waves obtained from posterior tibial artery resembled those of femoral artery rather than those of posterior tibial artery waves in adults. We conclude that radial and posterior tibial artery wave forms in neonates appear to have a central appearance. This phenomenon might be explained by the close proximity of the radial and posterior tibial artery to the central aorta and femoral artery respectively, due to the small and short limbs of the neonate. The finding allows an "easy central pressure look" at both ends of the neonatal aorta.

  6. Reciprocal spin Hall effects in conductors with strong spin-orbit coupling: a review

    NASA Astrophysics Data System (ADS)

    Niimi, Yasuhiro; Otani, YoshiChika

    2015-12-01

    Spin Hall effect and its inverse provide essential means to convert charge to spin currents and vice versa, which serve as a primary function for spintronic phenomena such as the spin-torque ferromagnetic resonance and the spin Seebeck effect. These effects can oscillate magnetization or detect a thermally generated spin splitting in the chemical potential. Importantly this conversion process occurs via the spin-orbit interaction, and requires neither magnetic materials nor external magnetic fields. However, the spin Hall angle, i.e. the conversion yield between the charge and spin currents, depends severely on the experimental methods. Here we discuss the spin Hall angle and the spin diffusion length for a variety of materials including pure metals such as Pt and Ta, alloys and oxides determined by the spin absorption method in a lateral spin valve structure.

  7. Spin-wave excitations induced by spin current in spin-valve structures

    NASA Astrophysics Data System (ADS)

    Liu, Haoliang; Sun, Dali; Zhang, Chuang; Groesbeck, Matthew; Vardeny, Zeev Valy; Department of Physics; Astronomy, University of Utah, Salt Lake City, Utah 84112, USA Team

    2016-03-01

    We have investigated the magnetization dynamics of NiFe/Pt/Co spin-valve structures with different Pt layer thickness, using a broadband ferromagnetic resonance (FMR) and Brillouin light scattering (BLS) at ambient temperature. We found that the Gilbert damping factor, α of the two ferromagnetic (FM) layer films in the spin-valve structure are significantly larger than α of each individual FM layer. We interpret the increase in α in the spin-valve configuration as due to an interaction between the FM layers mediated by the induced spin current through the Pt interlayer when FMR conditions are met for one of the FM. This was verified by BLS of the spin-valve structure, in which the magnons density in the adjacent FM layer is enhanced upon FMR of the other FM layer. We have studied this spin-current-mediated interaction as a function of the Pt interlayer. Work supported by the MURI-AFOSR Grant FA9550-14-1-0037, and the UofU facility center supported by NSF-MRSEC Grant DMR-1121252.

  8. Caliber-persistent labial artery.

    PubMed

    Lewis, David M

    2003-01-01

    Caliber-persistent labial artery presents as a soft tissue elevation of labial mucosa that can be bluish or normal in color, disappears when stretched, and pulsates on gentle palpation. Often the artery can be visualized through the stretched mucosa. Such lesions occur in an elderly population (average age = 58 years), are equally distributed between males and females, and are twice as common in the upper lip than in the lower (Figs. 4 & 5). The occurrence of multiple lesions has been reported, along with increased incidence of other vascular lesions. The [figure: see text] lesions are usually asymptomatic with a few being associated with surface ulceration. When the lesion is clinically mistaken for a mucocele, fibroma [figure: see text] or other vascular lesion and biopsied, brisk bleeding is encountered. PMID:12674712

  9. Human Arterial Ring Angiogenesis Assay.

    PubMed

    Seano, Giorgio; Primo, Luca

    2016-01-01

    In this chapter we describe a model of human angiogenesis where artery explants from umbilical cords are embedded in gel matrices and subsequently produce capillary-like structures. The human arterial ring (hAR) assay is an innovative system that enables three-dimensional (3D) and live studies of human angiogenesis. This ex vivo model has the advantage of recapitulating several steps of angiogenesis, including endothelial sprouting, migration, and differentiation into capillaries. Furthermore, it can be exploited for (1) identification of new genes regulating sprouting angiogenesis, (2) screening for pro- or anti-angiogenic drugs, (3) identification of biomarkers to monitor the efficacy of anti-angiogenic regimens, and (4) dynamic analysis of tumor microenvironmental effects on vessel formation. PMID:27172955

  10. Management of Carotid Artery Trauma

    PubMed Central

    Lee, Thomas S.; Ducic, Yadranko; Gordin, Eli; Stroman, David

    2014-01-01

    With increased awareness and liberal screening of trauma patients with identified risk factors, recent case series demonstrate improved early diagnosis of carotid artery trauma before they become problematio. There remains a need for unified screening criteria for both intracranial and extracranial carotid trauma. In the absence of contraindications, antithrombotic agents should be considered in blunt carotid artery injuries, as there is a significant risk of progression of vessel injury with observation alone. Despite CTA being used as a common screening modality, it appears to lack sufficient sensitivity. DSA remains to be the gold standard in screening. Endovascular techniques are becoming more widely accepted as the primary surgical modality in the treatment of blunt extracranial carotid injuries and penetrating/blunt intracranial carotid lessions. Nonetheless, open surgical approaches are still needed for the treatment of penetrating extracranial carotid injuries and in patients with unfavorable lesions for endovascular intervention. PMID:25136406

  11. Kondo spin screening cloud in two-dimensional electron gas with spin-orbit couplings.

    PubMed

    Feng, Xiao-Yong; Zhang, Fu-Chun

    2011-03-16

    A spin-1/2 Anderson impurity in a semiconductor quantum well with Rashba and Dresselhaus spin-orbit couplings is studied by using a variational wavefunction method. The local magnetic moment is found to be quenched at low temperatures. The spin-spin correlations of the impurity and the conduction electron density show anisotropy in both spatial and spin spaces, which interpolates the Kondo spin screenings of a conventional metal and of a surface of three-dimensional topological insulators.

  12. Ultrasonic Imaging Of Deep Arteries

    NASA Technical Reports Server (NTRS)

    Rooney, James A.; Heyser, Richard C.; Lecroissette, Dennis H.

    1990-01-01

    Swept-frequency sound replaces pulsed sound. Ultrasonic medical instrument produces images of peripheral and coronary arteries with resolutions higher and at depths greater than attainable by previous ultrasonic systems. Time-delay-spectrometry imager includes scanning, image-processing, and displaying equipment. It sweeps in frequency from 0 to 10 MHz in 20 ms, pauses for 5 ms, and repeats sweep. Intended for use in noninvasive detection and measurement of atherosclerotic lesions.

  13. Renal implications of arterial hypertension.

    PubMed

    Ruilope, L M

    1997-03-01

    Renal vascular damage caused by arterial hypertension participates in alterations of the systemic vascular function and structure. Nephrosclerosis seems to run in parallel with the systemic atherosclerosis that accounts for the increased cardiovascular morbidity and mortality seen in hypertensive patients. Parameters indicating the existence of an alteration in renal function (increased serum creatinine, proteinuria and microalbuminuria) are independent predictors for an increased cardiovascular morbidity and mortality. Hence, parameters of renal function must be considered in any stratification of cardiovascular risk in hypertensive patients.

  14. [Cerebral artery thrombosis in pregnancy].

    PubMed

    Charco Roca, L M; Ortiz Sanchez, V E; Hernandez Gutierrez-Manchon, O; Quesada Villar, J; Bonmatí García, L; Rubio Postigo, G

    2015-11-01

    A 28 year old woman, ASA I, who, in the final stages of her pregnancy presented with signs of neural deficit that consisted of distortion of the oral commissure, dysphagia, dysarthria, and weakness on the left side of the body. She was diagnosed with thrombosis in a segment of the right middle cerebral artery which led to an ischemic area in the right frontal lobe. Termination of pregnancy and conservative treatment was decided, with good resolution of the symptoms. PMID:25698610

  15. [Cerebral artery thrombosis in pregnancy].

    PubMed

    Charco Roca, L M; Ortiz Sanchez, V E; Hernandez Gutierrez-Manchon, O; Quesada Villar, J; Bonmatí García, L; Rubio Postigo, G

    2015-11-01

    A 28 year old woman, ASA I, who, in the final stages of her pregnancy presented with signs of neural deficit that consisted of distortion of the oral commissure, dysphagia, dysarthria, and weakness on the left side of the body. She was diagnosed with thrombosis in a segment of the right middle cerebral artery which led to an ischemic area in the right frontal lobe. Termination of pregnancy and conservative treatment was decided, with good resolution of the symptoms.

  16. Aneurysm of the Splenic Artery

    PubMed Central

    Bedford, P. D.; Lodge, Brian

    1960-01-01

    This paper records an incidence of 10·4% of aneurysm of the splenic artery in 250 consecutive routine post-mortem examinations. Medial degeneration seemed to be the commonest cause of such aneurysms and although a number were associated with other intraabdominal pathology, including portal hypertension, the association may be fortuitous and not causal. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6 PMID:13688586

  17. Immune Mechanisms in Arterial Hypertension.

    PubMed

    Wenzel, Ulrich; Turner, Jan Eric; Krebs, Christian; Kurts, Christian; Harrison, David G; Ehmke, Heimo

    2016-03-01

    Traditionally, arterial hypertension and subsequent end-organ damage have been attributed to hemodynamic factors, but increasing evidence indicates that inflammation also contributes to the deleterious consequences of this disease. The immune system has evolved to prevent invasion of foreign organisms and to promote tissue healing after injury. However, this beneficial activity comes at a cost of collateral damage when the immune system overreacts to internal injury, such as prehypertension. Renal inflammation results in injury and impaired urinary sodium excretion, and vascular inflammation leads to endothelial dysfunction, increased vascular resistance, and arterial remodeling and stiffening. Notably, modulation of the immune response can reduce the severity of BP elevation and hypertensive end-organ damage in several animal models. Indeed, recent studies have improved our understanding of how the immune response affects the pathogenesis of arterial hypertension, but the remarkable advances in basic immunology made during the last few years still await translation to the field of hypertension. This review briefly summarizes recent advances in immunity and hypertension as well as hypertensive end-organ damage.

  18. Arterial calcification: friend or foe?

    PubMed

    Nicoll, Rachel; Henein, Michael Y

    2013-07-31

    There is a significant relationship between the presence, extent and progression of coronary artery calcification (CAC) and cardiovascular (CV) events and mortality in both CV and renal patients and CAC scoring can provide improved predictive ability over risk factor scoring alone. There is also a close relationship between CAC presence and atherosclerotic plaque burden, with angiography studies showing very high sensitivity but poor specificity of CAC score for predicting obstructive disease. Nevertheless, there are objections to CAC screening because of uncertainties and lack of studies showing improved outcome. Furthermore, histopathology studies indicate that heavily calcified plaque is unlikely to result in a CV event, while the vulnerable plaque tends to be uncalcified or 'mixed', suggesting that calcification may be protective. This scenario highlights a number of paradoxes, which may indicate that the association between CAC and CV events is spurious, following from the adoption of CAC as a surrogate for high plaque burden, which itself is a surrogate for the presence of vulnerable plaque. Since studies indicate that arterial calcification is a complex, organised and regulated process similar to bone formation, there is no particular reason why it should be a reliable indicator of either the plaque burden or the risk of a future CV event. We suggest that it is time to divorce arterial calcification from atherosclerosis and to view it as a distinct pathology in its own right, albeit one which frequently coexists with atherosclerosis and is related to it for reasons which are not yet fully understood.

  19. Arterial endofibrosis in professional cyclists

    PubMed Central

    VERALDI, G.F.; MACRÌ, M.; CRISCENTI, P.; SCORSONE, L.; ZINGARETTI, C.C.; GNONI, M.; MEZZETTO, L.

    2015-01-01

    External Iliac Artery Endofibrosis (EIAE) is an uncommon disease usually affecting young, otherwise healthy, patients. It usually involves cyclists but cases have been reported in other groups of endurance athletes. The external iliac artery is the most affected anatomical site but other locations are described too. The precise pathophysiology and long-term evolution of the disease still remain unknown. The diagnosis may be challenging and delayed as the patients usually present symptoms only in extreme conditions and physical and instrumental examinations may be normal at rest. We present two cases of young professional cyclists who suffered of exercise-induced leg pain which led them to reduce running. Both patients were firstly treated with balloon angioplasty that rapidly failed to improve their symptoms. The successive open surgery with endofibrosectomy and autologous saphenous vein closure patch completely resolved physical limitations. EIAE is a rare disease that can induce arterial stenosis, thrombosis, dissection and secondary atheroma. After-exercise ankle-brachial index represents a useful diagnostic criterion. Careful observation of angio-CT may strengthen the suspect. Knowledge of the these features allows a better pre-operative assessment and an early effective treatment. Surgical revascularization remains the gold standard approach. PMID:26888703

  20. Anomalous Right Subclavian Artery Aneurysms

    PubMed Central

    Knight, Gordon C.; Codd, John E.

    1991-01-01

    During the past 2 years, 3 anomalous right subclavian artery aneurysms have been encountered at the St. Louis Heart Institute. The 1st patient, a 72-year-old woman, was found to have an asymptomatic 5-cm-diameter anomalous right subclavian artery aneurysm after surgery for suspected rupture of an abdominal aortic aneurysm. Resection was not attempted because of her poor cardiopulmonary and renal condition. One year later, the patient remains alive with marked cardiopulmonary limitations. The 2nd patient, a 77-year-old man, experienced dysphagia and severe weight loss because of a 14-cm-diameter aneurysm. Three days after undergoing surgical repair, he required reoperation for graft occlusion with right upper-extremity ischemia. Six months after hospital discharge, he died of pulmonary insufficiency and metastatic colon cancer. The 3rd patient, a 73-year-old woman, required emergency surgical intervention because of acute rupture and hypovolemic shock. Thirteen days later, she died of aspiration, asphyxia, and cardiac arrest. On the basis of our experience and a review of the literature, we conclude that symptomatic anomalous right subclavian artery aneurysms are rare, and that surgical intervention entails a relatively high morbidity and mortality rate. If long-term survival is anticipated, associated medical illnesses should be considered before surgery is undertaken. (Texas Heart Institute Journal 1991;18:209-18) Images PMID:15227483

  1. Growing collateral arteries on demand.

    PubMed

    Oh, Charles C; Klein, Jason D; Migrino, Raymond Q; Thornburg, Kent L

    2011-09-01

    Recent studies have significantly advanced our understanding of arteriogenesis, raising hope that therapies to increase collateral arterial formation may become important new tools in the treatment of ischemic disease. The most important initiating trigger for arteriogenesis is the marked increase in shear stress which is sensed by the endothelium and leads to characteristic changes. Intracellularly, it was shown that platelet endothelial cell adhesion molecule (PECAM-1) becomes tyrosine-phosphorylated in response to increased shear stress, suggesting a role as a possible mechanoreceptor for dynamic and continual monitoring of shear stress. The signal generated by PECAM-1 leads to the activation of the Rho pathway among others. More than 40 genes have been shown to have a shear stress responsive element. The Rho pathway is activated early and appears to be essential to the arteriogenic response as inhibiting it abolished the effect of fluid shear stress. Overexpression of a Rho pathway member, Actin-binding Rho protein (Abra), led to a 60% increase in collateral perfusion over simple femoral artery occlusion. A patent for the Abra gene has been filed recently. It may be a harbinger of a future where collateral arteries grown on demand may become an effective treatment for ischemic vascular disease. PMID:21861827

  2. Aberrant Ovarian Collateral Originating from External Iliac Artery During Uterine Artery Embolization

    SciTech Connect

    Kwon, Joon Ho; Kim, Man Deuk Lee, Kwang-hun; Lee, Myungsu; Lee, Mu Sook; Won, Jong Yun; Park, Sung Il; Lee, Do Yun

    2013-02-15

    We report a case of a 35-year-old woman who underwent uterine artery embolization (UAE) for symptomatic multiple uterine fibroids with collateral aberrant right ovarian artery that originated from the right external iliac artery. We believe that this is the first reported case in the literature of this collateral uterine flow by the right ovarian artery originated from the right external iliac artery. We briefly present the details of the case and review the literature on variations of ovarian artery origin that might be encountered during UAE.

  3. Anisotropic Absorption of Pure Spin Currents

    NASA Astrophysics Data System (ADS)

    Baker, A. A.; Figueroa, A. I.; Love, C. J.; Cavill, S. A.; Hesjedal, T.; van der Laan, G.

    2016-01-01

    Spin transfer in magnetic multilayers offers the possibility of ultrafast, low-power device operation. We report a study of spin pumping in spin valves, demonstrating that a strong anisotropy of spin pumping from the source layer can be induced by an angular dependence of the total Gilbert damping parameter, α , in the spin sink layer. Using lab- and synchrotron-based ferromagnetic resonance, we show that an in-plane variation of damping in a crystalline Co50 Fe50 layer leads to an anisotropic α in a polycrystalline Ni81 Fe19 layer. This anisotropy is suppressed above the spin diffusion length in Cr, which is found to be 8 nm, and is independent of static exchange coupling in the spin valve. These results offer a valuable insight into the transmission and absorption of spin currents, and a mechanism by which enhanced spin torques and angular control may be realized for next-generation spintronic devices.

  4. Anisotropic Absorption of Pure Spin Currents.

    PubMed

    Baker, A A; Figueroa, A I; Love, C J; Cavill, S A; Hesjedal, T; van der Laan, G

    2016-01-29

    Spin transfer in magnetic multilayers offers the possibility of ultrafast, low-power device operation. We report a study of spin pumping in spin valves, demonstrating that a strong anisotropy of spin pumping from the source layer can be induced by an angular dependence of the total Gilbert damping parameter, α, in the spin sink layer. Using lab- and synchrotron-based ferromagnetic resonance, we show that an in-plane variation of damping in a crystalline Co_{50}Fe_{50} layer leads to an anisotropic α in a polycrystalline Ni_{81}Fe_{19} layer. This anisotropy is suppressed above the spin diffusion length in Cr, which is found to be 8 nm, and is independent of static exchange coupling in the spin valve. These results offer a valuable insight into the transmission and absorption of spin currents, and a mechanism by which enhanced spin torques and angular control may be realized for next-generation spintronic devices. PMID:26871353

  5. Pure spin current in lateral structures

    NASA Astrophysics Data System (ADS)

    Chen, Shuhan

    Spintronics, a frontier academic research area, is advancing rapidly in recent years. It has been chosen as one of the promising candidates for overcoming the obstacles in continuing the "Moore's Law" of the electronics industry. Spintronics employs both spin and charge degrees of freedom of electrons to reduce energy consumption and increase the flexibility of IC design. To achieve this, it is extremely important to understand the generation, transport, and detection of the spin polarized current (spin current). In this work we use a mesoscopic metallic spintronic structure-nonlocal spin valve (NLSV)-for fundamental studies of spintronics. A nonlocal spin valve consists of two ferromagnetic electrodes (a spin injector and a spin detector) bridged by a non-magnetic spin channel. A thin aluminum oxide barrier (~ 2 - 3 nm) has been shown to effectively enhance the spin injection and detection polarizations. We have studied spin injection and detection in these nanoscale structures. Several topics will be discussed in this work. In Chapter 4 we explore spin transport in NLSVs with Ag channels. Substantial spin signals are observed. The temperature dependence of the spin signals indicates long spin diffusion lengths and low surface spin-flip rate in the mesoscopic Ag channels. Chapter 5 will focus on the asymmetric spin absorption across the low-resistance AlOx barriers in NLSVs. This effect allows for a more simplified and efficient detection scheme for the spin accumulation. Then in Chapter 6 we report a large spin signal owing to a highly resistive break-junction. We have also developed a model to describe the spin-charge coupling effect which enables the large spin signal. In the end, Spin Hall Effect (SHE) is investigated in Chapter 7. A mesoscopic Pt film is utilized to inject a spin accumulation into a mesoscopic Cu channel via the SHE. The spin accumulation in Cu can be detected by the nonlocal method. The reciprocal effect -- the inverse Spin Hall Effect - (i

  6. Is The Intrinsic Spin Hall Effect Measurable?

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoyang

    2005-03-01

    Despite of the large intrinsic spin Hall conductivity in a spin- orbit coupled material predicted theoretically, we show that the intrinsic spin Hall effect in any diffusive sample is not measurable via conventional transport methods, thus the research on the intrinsic spin Hall effect is limited at the pure theoretical content. After generally defining the intrinsic and extrinsic transport coefficients, we show that the intrinsic magnetization Hall current, which is the sum of the intrinsic spin and intrinsic orbit-angular-momentum Hall currents, is identically zero. More importantly, we demonstrate that the equation of motion for the spin density does not depend on the intrinsic spin Hall current, therefore the transverse spin accumulation is solely determined by the extrinsic spin Hall current. The zero intrinsic magnetization Hall current and the independence of the spin accumulation on the intrinsic spin Hall effect lead us to conclude that the intrinsic spin Hall effect can not be assessed by conventional spin transport experiments based on the measurement of the magnetization current and the spin accumulation at the edge of the sample.

  7. Spin transport in benzofurane bithiophene based organic spin valves

    SciTech Connect

    Palosse, Mathieu; Séguy, Isabelle; Bedel-Pereira, Élena; Villeneuve-Faure, Christina; Mallet, Charlotte; Frère, Pierre; Warot-Fonrose, Bénédicte; Biziere, Nicolas; Bobo, Jean-François

    2014-01-15

    In this paper we present spin transport in organic spin-valves using benzofurane bithiophene (BF3) as spacer layer between NiFe and Co ferromagnetic electrodes. The use of an AlO{sub x} buffer layer between the top electrode and the organic layer is discussed in terms of improvements of stacking topology, electrical transport and oxygen contamination of the BF3 layer. A study of magnetic hysteresis cycles evidences spin-valve behaviour. Transport properties are indicative of unshorted devices with non-linear I-V characteristics. Finally we report a magnetoresistance of 3% at 40 K and 10 mV in a sample with a 50 nm thick spacer layer, using an AlO{sub x} buffer layer.

  8. Controlling spin-spin network dynamics by repeated projective measurements

    PubMed Central

    Bretschneider, Christian O.; Álvarez, Gonzalo A.; Kurizki, Gershon; Frydman, Lucio

    2016-01-01

    We show that coupled-spin network manipulations can be made highly effective by repeated “projections” of the evolving quantum states onto diagonal density-matrix states (populations). As opposed to the intricately crafted pulse trains that are often used to fine-tune a complex network’s evolution, the strategy hereby presented derives from the “quantum-Zeno effect” and provides a highly robust route to guide the evolution by destroying all unwanted correlations (coherences). We exploit these effects by showing that a relaxation-like behaviour is endowed to polarization transfers occurring within a N-spin coupled network. Experimental implementations yield coupling constant determinations for complex spin-coupling topologies, as demonstrated within the field of liquid-state nuclear magnetic resonance (NMR). PMID:22540774

  9. Measurement of noncommuting spin components using spin-orbit interaction

    SciTech Connect

    Sokolovski, D.; Sherman, E. Ya.

    2011-09-15

    We propose a possible experiment aimed at a joint measurement of two noncommuting spin-1/2 components and analyze its physical meaning. We demonstrate that switching of a strong spin-orbit interaction, e.g., in a solid-state or a cold-atom system, for a short time interval simulates a simultaneous von Neumann measurement of the operators {sigma}{sub x} and {sigma}{sub y}. With the spin dynamics mapped onto the quantum coordinate-space motion, such an experiment determines averages of {sigma}{sub x} and {sigma}{sub y} over the duration of the measurement, however short the latter may be. These time averages, unlike the instantaneous values of {sigma}{sub x} and {sigma}{sub y}, may be evaluated simultaneously to an arbitrary accuracy.

  10. Octet spin fractions and the proton spin problem.

    PubMed

    Shanahan, P E; Thomas, A W; Tsushima, K; Young, R D; Myhrer, F

    2013-05-17

    The relatively small fraction of the spin of the proton carried by its quarks presents a major challenge to our understanding of the strong interaction. Traditional efforts to explore this problem have involved new and imaginative experiments and QCD based studies of the nucleon. We propose a new approach to the problem that exploits recent advances in lattice QCD. In particular, we extract values for the spin carried by the quarks in other members of the baryon octet in order to see whether the suppression observed for the proton is a general property or depends significantly on the baryon structure. We compare these results with the values for the spin fractions calculated within a model that includes the effects of confinement, relativity, gluon exchange currents, and the meson cloud required by chiral symmetry, finding a very satisfactory level of agreement given the precision currently attainable. PMID:25167398

  11. [Coronary revascularization by arterial bypasses: advantages, disadvantages].

    PubMed

    Bical, O; Deleuze, P; Sousa Uva, M

    1997-01-01

    Coronary vein grafts are frequently become occluded or develop atherosclerotic lesions in the long-term. In contrast, the internal mammary artery has a very satisfactory long-term patency rate. The use of an internal mammary artery on the LAD consequently increases the benefit of coronary surgery. The benefit of using 2 internal mammary arteries or other arterial grafts for coronary artery bypass surgery is more controversial. The advantages and disadvantages of the various coronary artery grafts are reported together with the clinical experience of several teams in this area. Coronary artery surgery should be reserved to patients with a good general condition, who are likely to benefit from this type of revascularization. The right internal mammary artery is unsuitable for revascularization of the right coronary network and the two internal mammary arteries must be used to revascularize the left coronary network, in order to obtain a good result. However, surgeons must be aware of the limitations of coronary artery surgery and these techniques should be used cautiously.

  12. Hereditary and environmental influences on arterial function.

    PubMed

    Hayward, C S; Benetos, A

    2007-07-01

    1. With the ageing population and increasing heart failure, arterial function has been shown to contribute to cardiovascular risk because of its adverse effects on ventriculovascular coupling. Population studies have confirmed independent prognostic information of arterial stiffening on cardiovascular survival. 2. The term 'arterial function' encompasses a range of phenotypes, including measures of arterial structure/remodelling, measures of arterial wall mechanics, surrogate measures of stiffness and of wave reflection. There exists significant interaction between these measures and none is truly independent of the others. Added to this complexity is the recognition that, although arterial function has a strong genetic component, quantification requires a range of techniques from twin to family and population studies. 3. The contribution of heritability is often derived from statistical models with input from genomic scanning and candidate gene studies. Studies to date confirm a significant heritable component for the majority of phenotypes examined. However, it has also been recognized that the factors involved in blood pressure maintenance are likely to be separate to those in arterial structural degeneration with ageing. Candidate genes for arterial function go beyond those of the sympathetic and renin-angiotensin systems and include genes involved in signalling pathways and extracellular matrix modulation. 4. The present review examines the evidence for heritability of the major arterial function phenotypes with environmental and ageing modulation. A brief overview of the impact of atherosclerotic risk factors on arterial function is included.

  13. Assessment of conduit artery vasomotion using photoplethysmography

    NASA Astrophysics Data System (ADS)

    Kanders, Karlis; Grabovskis, Andris; Marcinkevics, Zbignevs; Aivars, Juris Imants

    2013-11-01

    Vasomotion is a spontaneous oscillation of vascular tone. The phenomenon has been observed in small arterioles and capillaries as well as in the large conduit arteries. The layer of smooth muscle cells that surrounds a blood vessel can spontaneously and periodically change its tension and thereby the arterial wall stiffness also changes. As the understanding of the phenomenon is still rather obscure, researchers would benefit from a low-cost and reliable investigation technique such as photoplethysmography (PPG). PPG is an optical blood pulsation measurement technique that can offer substantial information about the arterial stiffness. The aims of this pilot study were to evaluate the usefulness of the PPG technique in the research of vasomotion and to investigate vasomotion in the relatively large conduit arteries. Continuous 15 minute long measurements of posterior tibial artery wall stiffness were taken. Artery diameter, electrocardiogram, blood pressure and respiration were also simultaneously registered. Fast Fourier Transform power spectra were calculated to identify unique stiffness oscillations that did not correspond to fluctuations in the systemic parameters and thus would indicate vasomotion. We concluded that photoplethysmography is a convenient method for the research of the vasomotion in large arteries. Local stiffness parameter b/a is more accurate to use and easier to measure than the pulse wave velocity which describes stiffness of a segment of an artery. Conduit arteries might exhibit a low amplitude high frequency vasomotion ( 9 to 27 cycles per minute). Low frequency vasomotion is problematic to distinguish from the passive oscillations imposed by the arterial pressure.

  14. Arterial Distensibility in Chronic Inflammatory Rheumatic Disorders

    PubMed Central

    Yildiz, Mustafa

    2010-01-01

    The pulse wave velocity (PWV), as an indicator of arterial distensibility, may play an important role in the stratification of patients based on the cardiovascular risk. PWV inversely correlates with arterial distensibility and relative arterial compliance. Decreased arterial distensibility alters arterial blood pressure and flow dynamics, and disturbes coronary perfusion. Systemic immune and inflammatory diseases, such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are associated with increased morbidity and mortality, predominantly due to adverse cardiovascular events. Systemic inflammation in these disorders may alter arterial compliance and arterial distensibility and, through this effect, lead to accelerated atherosclerosis. We have demonstrated an increase in the carotid-femoral (aortic) PWV that is a technique in which large artery elasticity is assessed from analysis of the peripheral arterial waveform, in patients with chronic inflammatory conditions such as RA, SLE, familial Mediterranean fever (FMF), Wegener’s granulomatosis (WG), sarcoidosis, psoriasis and psoriatic arthritis except Behçet’s disease (BD). In this review, the issue of arterial stiffness in RA, SLE, as well as WG, psoriasis, FMF, BD, sarcoidosis, systemic sclerosis (SS) and Takayasu's arteritis (TA) is overviewed. PMID:20461114

  15. Emergent spin electromagnetism induced by magnetization textures in the presence of spin-orbit interaction (invited)

    SciTech Connect

    Tatara, Gen; Nakabayashi, Noriyuki

    2014-05-07

    Emergent electromagnetic field which couples to electron's spin in ferromagnetic metals is theoretically studied. Rashba spin-orbit interaction induces spin electromagnetic field which is in the linear order in gradient of magnetization texture. The Rashba-induced effective electric and magnetic fields satisfy in the absence of spin relaxation the Maxwell's equations as in the charge-based electromagnetism. When spin relaxation is taken into account besides spin dynamics, a monopole current emerges generating spin motive force via the Faraday's induction law. The monopole is expected to play an important role in spin-charge conversion and in the integration of spintronics into electronics.

  16. Decoherence of nitrogen-vacancy defect spins in diamond from surface spins

    NASA Astrophysics Data System (ADS)

    Dominguez, Michael; Flatté, Michael E.

    In recent work, researchers measured the spin coherence time of intentionally-doped nitrogen-vacancy (NV) spin ensembles. The spin coherence times of these spins depends on their local environment, including their nearness to the surface of the material. We calculated the decoherence time of a deep spin within the material affected by the presence of a sheet of surface spins interacting with the deep spin through the dipolar interaction. These calculations describe the experimental measurements qualitatively, however quantitative agreement requires the assumption these spins extend deeper into the material from the surface layer.

  17. Optimization of spin injection and spin detection in lateral nanostructures by geometrical means

    NASA Astrophysics Data System (ADS)

    Stejskal, Ondřej; Hamrle, Jaroslav; Pištora, Jaromír; Otani, Yoshichika

    2016-09-01

    Lateral spin devices are an important concept in nowadays all-metallic spintronic devices. One of the key problems is to obtain large spin injection and detection efficiency. Several concepts has been envisaged, such as to use half-metallic ferromagnetic electrodes or spin-polarized interface barriers. Within this work, we address the optimization of spin devices (namely optimization of spin current density, spin current and spin accumulation) based on adjustment of the geometry (dimensions) of the lateral device, material selection of spin conductors, jointly with optimization of the interface resistance.

  18. Exact SU(2) symmetry and persistent spin helix in a spin-orbit coupled system.

    PubMed

    Bernevig, B Andrei; Orenstein, J; Zhang, Shou-Cheng

    2006-12-01

    Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constants, and for the [110] Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. This symmetry is robust against spin-independent disorder and interactions and is generated by operators whose wave vector depends on the coupling strength. It renders the spin lifetime infinite at this wave vector, giving rise to a persistent spin helix. We obtain the spin fluctuation dynamics at, and away from, the symmetry point and suggest experiments to observe the persistent spin helix.

  19. Detection and Control of Individual Nuclear Spins Using a Weakly Coupled Electron Spin

    SciTech Connect

    Taminiau, T.H.; Wagenaar, J.J.T.; van der Sar, T.; Jelezko, F.; Dobrovitski, Viatcheslav V.; Hanson, R.

    2012-09-28

    We experimentally isolate, characterize, and coherently control up to six individual nuclear spins that are weakly coupled to an electron spin in diamond. Our method employs multipulse sequences on the electron spin that resonantly amplify the interaction with a selected nuclear spin and at the same time dynamically suppress decoherence caused by the rest of the spin bath. We are able to address nuclear spins with interaction strengths that are an order of magnitude smaller than the electron spin dephasing rate. Our results provide a route towards tomography with single-nuclear-spin sensitivity and greatly extend the number of available quantum bits for quantum information processing in diamond.

  20. Anatomical variations of the human suprarenal arteries.

    PubMed

    Manso, J C; DiDio, L J

    2000-09-01

    This is on anatomical study of the suprarenal arteries and their variations in 30 cadavers aimed at providing in a subsequent article the anatomical basis of arterial segments of the gland. The suprarenal glands were supplied by 3 main groups of suprarenal arteries: superior, middle and inferior. Only the superior and the inferior groups were present in all cases, since the middle vessels appeared in only 93.3% +/- 4.6 of the cases. The superior group included on each side 4 arteries in males and 5 in females; the middle group presented only 1 artery on each side in both males and females, and the inferior group exhibited on each side 2 arteries in males and 1 artery in females. The most variable group was the middle one, the aortic origin being the most frequent but with a relatively low incidence (53.3% +/- 9.1 on the right and 46.7% +/- 9.1 on the left). The superior group originated from the posterior branch of the ipsilateral inferior phrenic artery in 83.3% +/- 6.8 on the right and 80% +/- 7.3 on the left. The arteries of the inferior group were branches of the ipsilateral renal artery in 70% +/- 8.4 on the right and 50% +/- 9.1 on the left. The origin of the middle suprarenal arteries from the trunk of the inferior phrenic artery on both sides (26.7% +/- 8.1 on the right and 36.7% +/- 8.8 on the left) should be considered relevant. The anatomical findings warrant a further investigation for the identification, illustration and nomenclature of arterial anatomicosurgical segments.